Fixed typos in Audio Classification Documentation

[Uvi-12]

Fixes #35261

• Fixed possessive form: "it's" corrected to "its" in reference to the MInDS-14 dataset.
• Corrected unit capitalization: "khz" updated to "kHz" for proper scientific notation.
• Added a comma for clarity: A missing comma was added to improve grammatical correctness in the sentence about the output_dir parameter.

[stevhliu]

Thanks for improving!

[Uvi-12]

Hi @stevhliu, While reviewing the documentation, I noticed a few areas where the clarity and quality could be enhanced. These aren't necessarily typos or errors, but rather improvements that could make the content easier to understand. Would it be okay for me to proceed with making these improvements?

[stevhliu]

Hi, feel free to open an issue describing your proposed improvements

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[Uvi-12]

Hi, feel free to open an issue describing your proposed improvements

Thank you, I will do as you said. For this PR I have made the changes as per your review. If everything looks good please proceed with merging the PR.