Add future annotations.

Author: dennwc

livekit-api/livekit/api/_service.py

@@ -1,3 +1,4 @@
+from __future__ import __annotations__
 from typing import Dict
 import aiohttp
 from abc import ABC
@@ -16,7 +17,7 @@ def __init__(
         self.api_secret = api_secret
 
     def _auth_header(
-        self, grants: VideoGrants, sip: SIPGrants = None
+        self, grants: VideoGrants, sip: SIPGrants | None = None
     ) -> Dict[str, str]:
         tok = AccessToken(self.api_key, self.api_secret).with_grants(grants)
         if sip is not None: