Fix not "import os" (sgl-project#6057)

Author: hnyls2002

python/sglang/srt/disaggregation/decode.py

@@ -21,6 +21,7 @@
 from __future__ import annotations
 
 import logging
+import os
 from collections import deque
 from dataclasses import dataclass
 from typing import TYPE_CHECKING, List, Optional, Tuple