Fix docs typos in callbacks.py

[imyhxy]

Fix small typos.

The modified lines keep reformatted and revert by 0-composite-3.sh in ultralytics/actions. Conflict between ruff and docformatter, so the console keep saying that there are files have been reformatted.

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🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Refinement of code comments in callback utility.

📊 Key Changes

• Corrected a typo in the class docstring.
• Removed an unnecessary double quote from a method docstring.

🎯 Purpose & Impact

• 📝 These changes improve code readability and documentation clarity.
• 🛠️ There is no direct impact on YOLOv5 functionality; this is a housekeeping update.

[imyhxy]

No reformat happening in this PR's Github Action

[glenn-jocher]

@imyhxy hello! Thank you for bringing this to our attention. It seems there's a conflict between our formatting tools. We'll look into the issue between ruff and docformatter to ensure consistent formatting in our automated checks. Your effort to improve the documentation is greatly appreciated! 🙌

For now, please ensure that your local formatting aligns with the project's style guidelines. You can refer to our documentation for guidance on contributing and code style. If you've already signed the CLA and your PR is ready, we'll review it for merging. Thanks again for your contribution to the YOLOv5 community! 🚀

[glenn-jocher]

@imyhxy awesome, good fixes!!