Fix the learning rate in an audio-classification example
Author: regisss
Pull request: yes

# What does this PR do?

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The learning rate should be `3e-4` in one of the PyTorch audio classification example according to the link to the corresponding run: https://huggingface.co/anton-l/wav2vec2-base-lang-id


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Comments:
_The documentation is not available anymore as the PR was closed or merged._

Gently pinging @sgugger for final approval

Thanks for the fix!