[Doc] Show that use_audio_in_video is supported in docs

[DarkLight1337]

Purpose

Address #30779 (comment) now that #27721 has been merged

Test Plan

Test Result

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[chatgpt-codex-connector]

Codex usage limits have been reached for code reviews. Please check with the admins of this repo to increase the limits by adding credits.

[mergify]

Documentation preview: https://vllm--30837.org.readthedocs.build/en/30837/

[gemini-code-assist]

Code Review

This pull request aims to update the documentation to indicate that use_audio_in_video is now supported for Qwen2.5-Omni and Qwen3-Omni models. While this might be true for the V2 engine, the changes are misleading as the codebase contains explicit TODO comments indicating that this feature is not yet supported on the V1 engine due to lack of support for interleaved modalities. I've left two critical comments suggesting to either restore the notes or update them to clarify that the feature is only available on the V2 engine. This will prevent confusion for users who are on the V1 engine.