Clean up import vllm in quantization/__init__.py (#4834)

python/sglang/srt/layers/quantization/awq.py

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 import logging
-from typing import Any, Dict, List, Optional, Union
+from typing import Any, Dict, List, Optional
 
 import torch
 from sgl_kernel import awq_dequantize