refac: modernize type annotations (PEP 604 / PEP 585)

backend/open_webui/retrieval/loaders/external_document.py

@@ -1,8 +1,9 @@
-import requests
-import logging, os
+import logging
+import os
 from typing import Iterator, List, Union
 from urllib.parse import quote
 
+import requests
 from langchain_core.document_loaders import BaseLoader
 from langchain_core.documents import Document
 from open_webui.utils.headers import include_user_info_headers