fix: stop auto decoding for audio datasets

[begumcig]

Description

The LibriSpeech nightly dataset was failing in our nightly workflow. Initially, we suspected the issue was caused by missing or incorrect audio decoding libraries, so we tried to address it from that angle.

After further investigation, we realized the root cause was different: our collate functions expect audio file names as input, not already-decoded audio data. To match this expectation, we disabled automatic decoding for audio files.

Related Issue

Fixes #(issue number)

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactor (no functional change)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Testing

• I added or updated tests covering my changes
• Existing tests pass locally (uv run pytest -m "cpu and not slow")

For full setup and testing instructions, see the Contributing Guide.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code, especially for agent-assisted changes
• I updated the documentation where necessary

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[gsprochette]

Looks great, thank you 💅