update docs for external tables to use external data configuration sc…

…hema (#6417) (#12337)

* update docs for external tables to use external data configuration schema

* add missing period

* Update mmv1/third_party/terraform/website/docs/r/bigquery_table.html.markdown

Co-authored-by: Scott Suarez <ScottSuarez@google.com>

* making notes in this block consistent

Co-authored-by: Scott Suarez <ScottSuarez@google.com>
Signed-off-by: Modular Magician <magic-modules@google.com>

Signed-off-by: Modular Magician <magic-modules@google.com>
Co-authored-by: Scott Suarez <ScottSuarez@google.com>

.changelog/6417.txt

@@ -0,0 +1,3 @@
+```release-note:none
+
+```

website/docs/r/bigquery_table.html.markdown

@@ -115,13 +115,17 @@ The following arguments are supported:
 * `labels` - (Optional) A mapping of labels to assign to the resource.
 
 * `schema` - (Optional) A JSON schema for the table.
+
     ~>**NOTE:** Because this field expects a JSON string, any changes to the
     string will create a diff, even if the JSON itself hasn't changed.
     If the API returns a different value for the same schema, e.g. it
     switched the order of values or replaced `STRUCT` field type with `RECORD`
     field type, we currently cannot suppress the recurring diff this causes.
     As a workaround, we recommend using the schema as returned by the API.
 
+    ~>**NOTE:**  When setting `schema` for `external_data_configuration`, please use
+    `external_data_configuration.schema` [documented below](#nested_external_data_configuration).
+
 * `time_partitioning` - (Optional) If specified, configures time-based
     partitioning for this table. Structure is [documented below](#nested_time_partitioning).