doc(automl): add example for creating a TablesClient for EU in docstring (#9825)

Local render result: https://screenshot.googleplex.com/P8Yat8M4zdF

Author: helinwang

packages/google-cloud-automl/google/cloud/automl_v1beta1/tables/tables_client.py

@@ -50,7 +50,7 @@ def __init__(
     ):
         """Constructor.
 
-        Example:
+        Example for US region:
             >>> from google.cloud import automl_v1beta1
             >>>
             >>> from google.oauth2 import service_account
@@ -60,6 +60,17 @@ def __init__(
             ...     project='my-project', region='us-central1')
             ...
 
+        Example for EU region:
+            >>> from google.cloud import automl_v1beta1
+            >>>
+            >>> from google.oauth2 import service_account
+            >>>
+            >>> client_options = {'api_endpoint': 'eu-automl.googleapis.com:443'}
+            >>> client = automl_v1beta1.TablesClient(
+            ...     credentials=service_account.Credentials.from_service_account_file('~/.gcp/account.json'),
+            ...     project='my-project', region='eu', client_options=client_options)
+            ...
+
         Args:
             project (Optional[str]): The project ID of the GCP project all
                 future calls will default to. Most methods take `project` as an