Update setup.cfg to description_file field

[glenn-jocher]

Resolve UserWarning: Usage of dash-separated 'description-file' will not be supported in future versions. Please use the underscore name 'description_file' instead

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Improved consistency in the setup.cfg configuration file.

📊 Key Changes

• Corrected the description-file key to description_file in setup.cfg.

🎯 Purpose & Impact

• Ensures compliance with the expected standard for setup configuration, which might prevent potential parsing errors by tools that read this file.
• This change has a minimal direct impact on users but maintains the quality and reliability of the codebase.