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/distributed/test_pp_cudagraph.py

@@ -1,16 +1,10 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-from __future__ import annotations
-
-from typing import TYPE_CHECKING
-
 import pytest
+from typing_extensions import LiteralString
 
 from ..utils import compare_two_settings, create_new_process_for_each_test
 
-if TYPE_CHECKING:
-    from typing_extensions import LiteralString
-
 
 @pytest.mark.parametrize(
     "PP_SIZE, MODEL_NAME",