Update api/core/rag/extractor/pdf_extractor.py

The use of 'datetime.UTC' may lead to errors since the standard library typically uses 'datetime.timezone.utc'. Consider updating for compatibility.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

api/core/rag/extractor/pdf_extractor.py

@@ -122,10 +122,10 @@ class PdfExtractor(BaseExtractor):
                                     mime_type=mime_type or "",
                                     created_by=self._user_id,
                                     created_by_role=CreatedByRole.ACCOUNT,
-                                    created_at=datetime.datetime.now(datetime.UTC).replace(tzinfo=None),
+                                    created_at=datetime.datetime.now(datetime.timezone.utc).replace(tzinfo=None),
                                     used=True,
                                     used_by=self._user_id,
-                                    used_at=datetime.datetime.now(datetime.UTC).replace(tzinfo=None)
+                                    used_at=datetime.datetime.now(datetime.timezone.utc).replace(tzinfo=None)
                                 )
 
                                 db.session.add(upload_file)