Updating api summaries to reflect preview state (#28384)

* Updating api summaries to reflect preview state

* Updating naming of marketplace apis

specification/marketplacecatalog/resource-manager/Keys/stable/2023-01-01-preview/discoveryKeys.json

@@ -18,7 +18,7 @@
         "tags": [
           "CreateApiKey"
         ],
-        "summary": "Generates an API key, granting access to the full range of Marketplace Catalog APIs. Please note that a valid subscription is required to utilize this functionality.",
+        "summary": "Generates an API key, granting access to the full range of Marketplace Catalog APIs. Please note that this API is currently in a preview state and requires sign-up to the 'Discovery Api Key Early Access' preview feature using a valid Azure subscription. For more information on this process please see the documentation for Marketplace Catalog APIs [here](https://learn.microsoft.com/en-us/rest/api/marketplacecatalog/dataplane/products/get?view=rest-marketplacecatalog-dataplane-2023-05-01-preview&tabs=HTTP)",
         "operationId": "CreateApiKey_Post",
         "x-ms-examples": {
           "Create_Key": {
@@ -71,7 +71,7 @@
         "tags": [
           "RevokeApiKey"
         ],
-        "summary": "Revokes an active API key.",
+        "summary": "Revokes an active API key. Please note that this API is currently in a preview state and requires sign-up to the 'Discovery Api Key Early Access' preview feature using a valid Azure subscription. For more information on this process please see the documentation for Marketplace Catalog APIs [here](https://learn.microsoft.com/en-us/rest/api/marketplacecatalog/dataplane/products/get?view=rest-marketplacecatalog-dataplane-2023-05-01-preview&tabs=HTTP)",
         "operationId": "RevokeApiKey_Post",
         "x-ms-examples": {
           "Revoke_Key": {
@@ -120,7 +120,7 @@
         "tags": [
           "GetApiKeys"
         ],
-        "summary": "Retrieves a list of API keys associated with a selected subscription.",
+        "summary": "Retrieves a list of API keys associated with a selected subscription. Please note that this API is currently in a preview state and requires sign-up to the 'Discovery Api Key Early Access' preview feature using a valid Azure subscription. For more information on this process please see the documentation for Marketplace Catalog APIs [here](https://learn.microsoft.com/en-us/rest/api/marketplacecatalog/dataplane/products/get?view=rest-marketplacecatalog-dataplane-2023-05-01-preview&tabs=HTTP)",
         "operationId": "GetApiKeys_List",
         "x-ms-examples": {
           "Get_Key": {