fix(automl): fix typo in code example for AutoML Tables (#9806)

Typo in AutoML Tables code example at https://googleapis.dev/python/automl/latest/gapic/v1beta1/tables.html

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

@@ -56,7 +56,7 @@ def __init__(
             >>> from google.oauth2 import service_account
             >>>
             >>> client = automl_v1beta1.TablesClient(
-            ...     credentials=service_account.Credentials.from_service_account_file('~/.gcp/account.json')
+            ...     credentials=service_account.Credentials.from_service_account_file('~/.gcp/account.json'),
             ...     project='my-project', region='us-central1')
             ...