Fix/ignore economy dataset (#1043)

Co-authored-by: jyong <jyong@dify.ai>

api/events/event_handlers/create_document_index.py

@@ -1,6 +1,5 @@
 from events.dataset_event import dataset_was_deleted
 from events.event_handlers.document_index_event import document_index_created
-from tasks.clean_dataset_task import clean_dataset_task
 import datetime
 import logging
 import time