[Frontend] Remove print left in FrontendArgs.add_cli_args

[mgoin]

I suddenly started seeing these weird {'default': ['*'], 'help': 'Allowed origins.', 'type': <class 'str'>, 'nargs': '+'} logs on main.

vllm serve RedHatAI/Mistral-Small-3.1-24B-Instruct-2503-quantized.w4a16 --load-format=dummy
INFO 07-15 12:45:46 [__init__.py:253] Automatically detected platform cuda.
{'default': ['*'], 'help': 'Allowed origins.', 'type': <class 'str'>, 'nargs': '+'}
INFO 07-15 12:45:48 [api_server.py:1637] vLLM API server version 0.9.2rc2.dev155+g5b6fe23d0
{'default': ['*'], 'help': 'Allowed origins.', 'type': <class 'str'>, 'nargs': '+'}
INFO 07-15 12:45:48 [cli_args.py:268] non-default args: {'model': 'RedHatAI/Mistral-Small-3.1-24B-Instruct-2503-quantized.w4a16', 'load_format': 'dummy'}
...

It seems #20206 had left a print statement behind from debugging, so this PR removes it.

Now I see the expected:

vllm serve RedHatAI/Mistral-Small-3.1-24B-Instruct-2503-quantized.w4a16 --load-format=dummy
INFO 07-15 13:38:10 [__init__.py:253] Automatically detected platform cuda.
INFO 07-15 13:38:12 [api_server.py:1637] vLLM API server version 0.9.2rc2.dev155+g5b6fe23d0
INFO 07-15 13:38:12 [cli_args.py:267] non-default args: {'model': 'RedHatAI/Mistral-Small-3.1-24B-Instruct-2503-quantized.w4a16', 'load_format': 'dummy'}

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[gemini-code-assist]

Code Review

This pull request correctly removes a leftover debugging print statement from vllm/entrypoints/openai/cli_args.py. The change is straightforward and resolves the issue of unintended logs as described. The code is clean and ready to be merged.

[mgoin]

@simon-mo @DarkLight1337 could this get a force merge please?