fix(serviceusage): update the API

#### serviceusage:v1
The following keys were changed:
- schemas.MetricDescriptor.description

#### serviceusage:v1beta1
The following keys were changed:
- schemas.MetricDescriptor.description

discovery/serviceusage-v1.json

@@ -426,7 +426,7 @@
       }
     }
   },
-  "revision": "20200708",
+  "revision": "20200711",
   "rootUrl": "https://serviceusage.googleapis.com/",
   "schemas": {
     "AdminQuotaPolicy": {
@@ -1859,7 +1859,7 @@
       "type": "object"
     },
     "MetricDescriptor": {
-      "description": "Defines a metric type and its schema. Once a metric descriptor is created,\ndeleting or altering it stops data collection and makes the metric type's\nexisting data unusable.\n\nThe following are specific rules for service defined Monitoring metric\ndescriptors:\n\n* `type`, `metric_kind`, `value_type`, `description`, `display_name`,\n  `launch_stage` fields are all required. The `unit` field must be specified\n  if the `value_type` is any of DOUBLE, INT64, DISTRIBUTION.\n* Maximum of default 500 metric descriptors per service is allowed.\n* Maximum of default 10 labels per metric descriptor is allowed.\n\nThe default maximum limit can be overridden. Please follow\nhttps://cloud.google.com/monitoring/quotas",
+      "description": "Defines a metric type and its schema. Once a metric descriptor is created,\ndeleting or altering it stops data collection and makes the metric type's\nexisting data unusable.\n\nThe following are specific rules for service defined Monitoring metric\ndescriptors:\n\n* `type`, `metric_kind`, `value_type`, `description`, and `display_name`\n  fields are all required. The `unit` field must be specified\n  if the `value_type` is any of DOUBLE, INT64, DISTRIBUTION.\n* Maximum of default 500 metric descriptors per service is allowed.\n* Maximum of default 10 labels per metric descriptor is allowed.\n\nThe default maximum limit can be overridden. Please follow\nhttps://cloud.google.com/monitoring/quotas",
       "id": "MetricDescriptor",
       "properties": {
         "description": {

discovery/serviceusage-v1beta1.json

@@ -819,7 +819,7 @@
       }
     }
   },
-  "revision": "20200708",
+  "revision": "20200711",
   "rootUrl": "https://serviceusage.googleapis.com/",
   "schemas": {
     "AdminQuotaPolicy": {
@@ -2346,7 +2346,7 @@
       "type": "object"
     },
     "MetricDescriptor": {
-      "description": "Defines a metric type and its schema. Once a metric descriptor is created,\ndeleting or altering it stops data collection and makes the metric type's\nexisting data unusable.\n\nThe following are specific rules for service defined Monitoring metric\ndescriptors:\n\n* `type`, `metric_kind`, `value_type`, `description`, `display_name`,\n  `launch_stage` fields are all required. The `unit` field must be specified\n  if the `value_type` is any of DOUBLE, INT64, DISTRIBUTION.\n* Maximum of default 500 metric descriptors per service is allowed.\n* Maximum of default 10 labels per metric descriptor is allowed.\n\nThe default maximum limit can be overridden. Please follow\nhttps://cloud.google.com/monitoring/quotas",
+      "description": "Defines a metric type and its schema. Once a metric descriptor is created,\ndeleting or altering it stops data collection and makes the metric type's\nexisting data unusable.\n\nThe following are specific rules for service defined Monitoring metric\ndescriptors:\n\n* `type`, `metric_kind`, `value_type`, `description`, and `display_name`\n  fields are all required. The `unit` field must be specified\n  if the `value_type` is any of DOUBLE, INT64, DISTRIBUTION.\n* Maximum of default 500 metric descriptors per service is allowed.\n* Maximum of default 10 labels per metric descriptor is allowed.\n\nThe default maximum limit can be overridden. Please follow\nhttps://cloud.google.com/monitoring/quotas",
       "id": "MetricDescriptor",
       "properties": {
         "description": {

src/apis/serviceusage/v1.ts

@@ -1143,7 +1143,7 @@ export namespace serviceusage_v1 {
     syntax?: string | null;
   }
   /**
-   * Defines a metric type and its schema. Once a metric descriptor is created, deleting or altering it stops data collection and makes the metric type's existing data unusable.  The following are specific rules for service defined Monitoring metric descriptors:  * `type`, `metric_kind`, `value_type`, `description`, `display_name`,   `launch_stage` fields are all required. The `unit` field must be specified   if the `value_type` is any of DOUBLE, INT64, DISTRIBUTION. * Maximum of default 500 metric descriptors per service is allowed. * Maximum of default 10 labels per metric descriptor is allowed.  The default maximum limit can be overridden. Please follow https://cloud.google.com/monitoring/quotas
+   * Defines a metric type and its schema. Once a metric descriptor is created, deleting or altering it stops data collection and makes the metric type's existing data unusable.  The following are specific rules for service defined Monitoring metric descriptors:  * `type`, `metric_kind`, `value_type`, `description`, and `display_name`   fields are all required. The `unit` field must be specified   if the `value_type` is any of DOUBLE, INT64, DISTRIBUTION. * Maximum of default 500 metric descriptors per service is allowed. * Maximum of default 10 labels per metric descriptor is allowed.  The default maximum limit can be overridden. Please follow https://cloud.google.com/monitoring/quotas
    */
   export interface Schema$MetricDescriptor {
     /**

src/apis/serviceusage/v1beta1.ts

@@ -1227,7 +1227,7 @@ export namespace serviceusage_v1beta1 {
     syntax?: string | null;
   }
   /**
-   * Defines a metric type and its schema. Once a metric descriptor is created, deleting or altering it stops data collection and makes the metric type's existing data unusable.  The following are specific rules for service defined Monitoring metric descriptors:  * `type`, `metric_kind`, `value_type`, `description`, `display_name`,   `launch_stage` fields are all required. The `unit` field must be specified   if the `value_type` is any of DOUBLE, INT64, DISTRIBUTION. * Maximum of default 500 metric descriptors per service is allowed. * Maximum of default 10 labels per metric descriptor is allowed.  The default maximum limit can be overridden. Please follow https://cloud.google.com/monitoring/quotas
+   * Defines a metric type and its schema. Once a metric descriptor is created, deleting or altering it stops data collection and makes the metric type's existing data unusable.  The following are specific rules for service defined Monitoring metric descriptors:  * `type`, `metric_kind`, `value_type`, `description`, and `display_name`   fields are all required. The `unit` field must be specified   if the `value_type` is any of DOUBLE, INT64, DISTRIBUTION. * Maximum of default 500 metric descriptors per service is allowed. * Maximum of default 10 labels per metric descriptor is allowed.  The default maximum limit can be overridden. Please follow https://cloud.google.com/monitoring/quotas
    */
   export interface Schema$MetricDescriptor {
     /**