[router][CI] Clean up imports and prints statements in sgl-router/py_test (#12024)

sgl-router/py_test/unit/test_arg_parser.py

@@ -5,9 +5,7 @@ These tests focus on testing the argument parsing logic in isolation,
 without starting actual router instances.
 """
 
-import argparse
 from types import SimpleNamespace
-from unittest.mock import MagicMock, patch
 
 import pytest
 from sglang_router.launch_router import RouterArgs, parse_router_args