refactor: replace deprecated datetime.utcnow()

Signed-off-by: Rongrong <[email protected]>

src/command/inner/sub.py

@@ -20,7 +20,7 @@
 
 import re
 import asyncio
-from datetime import datetime
+from datetime import datetime, timezone
 from bs4 import BeautifulSoup
 from bs4.element import SoupStrainer
 from urllib.parse import urljoin
@@ -298,7 +298,7 @@ async def export_opml(user_id: int) -> Optional[bytes]:
     sub_list = await list_sub(user_id)
     opml = BeautifulSoup(OPML_TEMPLATE, 'lxml-xml')
     create_time = opml.new_tag('dateCreated')
-    create_time.string = opml.new_string(datetime.utcnow().strftime('%a, %d %b %Y %H:%M:%S UTC'))
+    create_time.string = opml.new_string(datetime.now(timezone.utc).strftime('%a, %d %b %Y %H:%M:%S UTC'))
     opml.head.append(create_time)
     empty_flags = True
     for _sub in sub_list: