[Misc] Replace Optional[X] with X | None syntax (#33332)

Signed-off-by: carlory <baofa.fan@daocloud.io>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

vllm/model_executor/layers/quantization/mxfp4.py

@@ -1,7 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 from enum import Enum
-from typing import Optional
 
 import torch
 from torch.nn.parameter import Parameter
@@ -197,7 +196,7 @@ class Mxfp4Config(QuantizationConfig):
 
     def get_quant_method(
         self, layer: torch.nn.Module, prefix: str
-    ) -> Optional["QuantizeMethodBase"]:
+    ) -> "QuantizeMethodBase | None":
         if isinstance(layer, LinearBase):
             if self.ignored_layers and is_layer_skipped(
                 prefix=prefix,