[Lint] Add python/sglang to ruff F401 checks and remove unused imports in files (#11685)

python/sglang/srt/server_args_config_parser.py

@@ -5,7 +5,7 @@ Handles merging of YAML configuration files with command-line arguments.
 
 import logging
 from pathlib import Path
-from typing import Any, Dict, List, Union
+from typing import Any, Dict, List
 
 import yaml