[Misc] Clean up utils (#27552)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

vllm/entrypoints/openai/api_server.py

@@ -108,7 +108,8 @@ from vllm.entrypoints.utils import (
 from vllm.logger import init_logger
 from vllm.reasoning import ReasoningParserManager
 from vllm.usage.usage_lib import UsageContext
-from vllm.utils import Device, FlexibleArgumentParser, set_ulimit
+from vllm.utils import Device, set_ulimit
+from vllm.utils.argparse_utils import FlexibleArgumentParser
 from vllm.utils.network_utils import is_valid_ipv6_address
 from vllm.utils.system_utils import decorate_logs
 from vllm.v1.engine.exceptions import EngineDeadError