Remove deprecated arg in vllm serve command

[meiyeh123]

Description

Remove --guided-decoding-backend "xgrammar" when vllm serve in mm_bench_recipe.sh

Tests

Already tested it

Checklist

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• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have made or will make corresponding changes to any relevant documentation.

[github-actions]

Description

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the past.

The rest of the description includes relevant details and context, examples:

• why is this change being made,
• the problem being solved and any relevant context,
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Tests

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Checklist

Before submitting this PR, please make sure:

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have made or will make corresponding changes to any relevant documentation.

[jcyang43]

Thanks. The guided-decoding-backend arg has been deprecated by the upstream in this PR