Chore: replace deprecated datetime.utcnow() with naive_utc_now() (#23312)

Signed-off-by: Yongtao Huang <yongtaoh2022@gmail.com>

api/services/dataset_service.py

@@ -266,7 +266,7 @@ class DatasetService:
                     "No Embedding Model available. Please configure a valid provider in the Settings -> Model Provider."
                 )
             except ProviderTokenNotInitError as ex:
-                raise ValueError(f"The dataset in unavailable, due to: {ex.description}")
+                raise ValueError(f"The dataset is unavailable, due to: {ex.description}")
 
     @staticmethod
     def check_embedding_model_setting(tenant_id: str, embedding_model_provider: str, embedding_model: str):
@@ -370,7 +370,7 @@ class DatasetService:
             raise ValueError("External knowledge api id is required.")
         # Update metadata fields
         dataset.updated_by = user.id if user else None
-        dataset.updated_at = datetime.datetime.utcnow()
+        dataset.updated_at = naive_utc_now()
         db.session.add(dataset)
 
         # Update external knowledge binding