delete segment not commit (#309)

api/tasks/clean_document_task.py

 
         for segment in segments:
             db.session.delete(segment)
-
+        db.session.commit()
         end_at = time.perf_counter()
         logging.info(
             click.style('Cleaned document when document deleted: {} latency: {}'.format(document_id, end_at - start_at), fg='green'))

api/tasks/document_indexing_update_task.py

 
         for segment in segments:
             db.session.delete(segment)
-
+        db.session.commit()
         end_at = time.perf_counter()
         logging.info(
             click.style('Cleaned document when document update data source or process rule: {} latency: {}'.format(document_id, end_at - start_at), fg='green'))