Update export.py, yolo.py sys.path.append()

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Improved module import paths and activation functions in export script.

📊 Key Changes

• Refactored sys.path.append to use a cleaner, more consistent style.
• Direct import statements for Conv and Detect classes instead of importing the entire models module.
• Changed activation assignments in Conv to use export-friendly versions when exporting models.

🎯 Purpose & Impact

• ✨ Maintainability: Using direct imports and cleaner paths makes the code more readable and easier to maintain.
• 🔥 Compatibility: Including export-specific activations ensures compatibility with various export formats.
• 🚀 User Experience: These changes may contribute to smoother model exports, benefiting users who deploy YOLOv5 models across different platforms.