Remove duplicate line in setup.cfg

[zldrobit]

I found that W504 rule of flake8 in setup.cfg is duplicated, so I send this PR to remove the second W504 rule.

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Improved Code Quality by Removing Redundant Lint Exception.

📊 Key Changes

• Eliminated a duplicate lint exception (W504 line break after binary operator).

🎯 Purpose & Impact

• Purpose: To clean up the setup.cfg file by removing unnecessary repetition, which may have been a minor oversight.
• Impact: Maintainers and contributors will work with a cleaner configuration file. No direct impact on end users, but it contributes to maintaining high standards in code quality and readability. 🛠️

[glenn-jocher]

@zldrobit PR is merged. Thank you for your contributions to YOLOv5 🚀 and Vision AI ⭐