fix(retail): add region tag for Python - Update purge user events (#13496)

* Update search_with_pagination.py

* Update purge_user_event.py

Author: rebeccaellis

retail/interactive-tutorials/events/purge_user_event.py

@@ -15,6 +15,8 @@
 
 # Deleting user event using Retail API.
 #
+# [START retail_purge_user_events]
+
 import google.auth
 from google.cloud.retail import PurgeUserEventsRequest, UserEventServiceClient
 
@@ -48,6 +50,8 @@ def call_purge_user_events():
     print("---the purge operation was started:----")
     print(purge_operation.operation.name)
 
+# [END retail_purge_user_events]
+
 
 write_user_event(visitor_id)
 call_purge_user_events()