[bugfix] fix the wrong parser

[reidliu41]

As I understand correctly(pls correct me if am wrong), there is no arg for collect_env, but it will show lots of args from --help, seems returen the wrong parser:

vllm collect-env --help
usage: vllm collect-env

Start collecting environment information.

options:
  --allow-credentials   Allow credentials. (default: False)
  --allowed-headers ALLOWED_HEADERS
                        Allowed headers. (default: ['*'])
  --allowed-methods ALLOWED_METHODS
                        Allowed methods. (default: ['*'])
  --allowed-origins ALLOWED_ORIGINS
                        Allowed origins. (default: ['*'])
  --api-key API_KEY     If provided, the server will require this key to be presented in the
                        header. (default: None)
  --chat-template CHAT_TEMPLATE
...

So it should simply return serve_parser, it may not show args in help.

 vllm collect-env --help
usage: vllm collect-env

Start collecting environment information.

options:
  -h, --help  show this help message and exit

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[reidliu41]

cc @DarkLight1337