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/kernels/attention/test_cascade_flash_attn.py

@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
-from typing import Optional
 
 import pytest
 import torch
@@ -85,7 +84,7 @@ def test_cascade(
     head_size: int,
     dtype: torch.dtype,
     block_size: int,
-    soft_cap: Optional[float],
+    soft_cap: float | None,
     num_blocks: int,
     fa_version: int,
 ) -> None: