Rename 'MacOS' to 'macOS'

[glenn-jocher]

Fix capitalization, i.e. https://www.apple.com/macos/monterey/

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated documentation and code references from 'MacOS' to 'macOS' for consistency.

📊 Key Changes

• Changed references from 'MacOS' to 'macOS' in various files:
  • .github/workflows/greetings.yml
  • detect.py
  • export.py
  • tutorial.ipynb
  • utils/loggers/wandb/README.md
  • val.py

🎯 Purpose & Impact

• Ensures consistent naming conventions across the project documentation and code comments.
• Enhances readability and professionalism in official project communications.
• Minimal to no impact on the functionality of the software, but improves the overall user experience when interacting with the repository and understanding the platform compatibility. 🍏🔄