Update Optional[x] -> x | None and Union[x, y] to x | y (#26633)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

tests/entrypoints/openai/test_async_tokenization.py

@@ -3,7 +3,7 @@
 
 import asyncio
 import random
-from typing import Callable
+from collections.abc import Callable
 
 import openai
 import pytest