Clean up imports (#5467)

python/sglang/srt/_custom_ops.py

@@ -1,10 +1,8 @@
 # Adapted from https://github.com/vllm-project/vllm/blob/v0.6.4.post1/vllm/_custom_ops.py
 import logging
-import os
 from typing import List, Tuple
 
 import torch
-import torch.library
 
 from sglang.srt.utils import get_bool_env_var, is_hip, is_hpu