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/models/multimodal/generation/vlm_utils/custom_inputs.py

@@ -2,7 +2,7 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 """Custom input builders for edge-cases in different models."""
 
-from typing import Callable
+from collections.abc import Callable
 
 from vllm.assets.image import ImageAsset
 from vllm.multimodal.image import rescale_image_size