refactor: simplify success response in dataset API endpoints by returning status code 204 directly (#19685)

api/controllers/service_api/dataset/dataset.py

         try:
             if DatasetService.delete_dataset(dataset_id_str, current_user):
                 DatasetPermissionService.clear_partial_member_list(dataset_id_str)
-                return {"result": "success"}, 204
+                return 204
             else:
                 raise NotFound("Dataset not found.")
         except services.errors.dataset.DatasetInUseError:

api/controllers/service_api/dataset/document.py

         except services.errors.document.DocumentIndexingError:
             raise DocumentIndexingError("Cannot delete document during indexing.")
 
-        return {"result": "success"}, 204
+        return 204
 
 
 class DocumentListApi(DatasetApiResource):

api/controllers/service_api/dataset/segment.py

         if not segment:
             raise NotFound("Segment not found.")
         SegmentService.delete_segment(segment, document, dataset)
-        return {"result": "success"}, 204
+        return 204
 
     @cloud_edition_billing_resource_check("vector_space", "dataset")
     def post(self, tenant_id, dataset_id, document_id, segment_id):
         except ChildChunkDeleteIndexServiceError as e:
             raise ChildChunkDeleteIndexError(str(e))
 
-        return {"result": "success"}, 204
+        return 204
 
     @cloud_edition_billing_resource_check("vector_space", "dataset")
     @cloud_edition_billing_knowledge_limit_check("add_segment", "dataset")