[Docs] Fix issues with e2e audio tutorial

[crypdick]

Why are these changes needed?

The audio tutorial is flaky: sometimes it runs to completion, sometimes it doesn't.

Related issue number

NA

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[Copilot]

Pull Request Overview

This PR aims to resolve flakiness in the e2e audio tutorial by modifying configuration values in the notebook example.

• Updated the value of "guided_decoding_backend" from "auto" to "xgrammar"
• Adjusted configuration in the README notebook to improve tutorial stability

Comments suppressed due to low confidence (1)

doc/source/ray-overview/examples/e2e-audio/README.ipynb:289

• Verify that 'xgrammar' is supported by downstream components and is intended for use here. If it's experimental or subject to change, consider adding documentation notes on its usage.

    "        \"guided_decoding_backend\": \"xgrammar\",\n",

[crypdick]

Tested both the release tests and ran the notebook manually to confirm the fix

[angelinalg]

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