Manually pick moshi requirements update from #15180

[GregoryComer]

Summary

The torchcodec nightly version we are pinning is out of retention. It was updated on main as part of #15180. This PR picks just that change to the requirements file to avoid picking up all of the other large changes in the PR. The follow-up change to the ffmpeg install in #15821 is also picked here, since it's needed for the previous change to work.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15879

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❌ 1 New Failure, 2 Cancelled Jobs

As of commit 51e9e14 with merge base e0dda90 ():

NEW FAILURE - The following job has failed:

• pull / test-openvino-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 85d2cd3fe74925b86ed94636fff9b4322ed0b93a6f7f5739f3adcaeda4d526f5 /exec failed with exit code 1

CANCELLED JOBS - The following jobs were cancelled. Please retry:

• pull / unittest / macos / macos-job (gh)
  ##[error]The operation was canceled.
• pull / unittest-editable / macos / macos-job (gh)
  ##[error]The operation was canceled.

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[GregoryComer]

Note that the OpenVINO failure is pre-existing (fixed in #15880).