chore: fix some unmatched region tags (GoogleCloudPlatform#4584)

part of GoogleCloudPlatform#4549

Author: Takashi Matsuo

appengine/standard_python3/building-an-app/building-an-app-1/main.py

@@ -41,4 +41,4 @@ def root():
     # http://flask.pocoo.org/docs/1.0/quickstart/#static-files. Once deployed,
     # App Engine itself will serve those files as configured in app.yaml.
     app.run(host='127.0.0.1', port=8080, debug=True)
-# [START gae_python38_render_template]
+# [END gae_python38_render_template]

iam/api-client/service_accounts.py

@@ -21,7 +21,7 @@
 
 import argparse
 # [START iam_create_service_account]
-# [START iam_list_service_account]
+# [START iam_list_service_accounts]
 # [START iam_rename_service_account]
 # [START iam_disable_service_account]
 # [START iam_enable_service_account]

spanner/cloud-client/snippets.py

@@ -762,7 +762,7 @@ def query_struct_field(instance_id, database_id):
 
     for row in results:
         print(u'SingerId: {}'.format(*row))
-# [START spanner_field_access_on_struct_parameters]
+# [END spanner_field_access_on_struct_parameters]
 
 
 # [START spanner_field_access_on_nested_struct_parameters]