Update links

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated documentation for installing the ultralytics package.

📊 Key Changes

• Changed the reference link for ultralytics package requirements from a requirements.txt file to pyproject.toml.

🎯 Purpose & Impact

• Improved Clarity: The update provides a more modern and standard way to list package requirements, aligning with Python packaging best practices.
• Easier Maintenance: Using pyproject.toml for dependencies makes it simpler to manage and update the library's requirements.
• Potential User Impact: Users installing the package will now refer to the more current pyproject.toml for dependencies, ensuring compatibility and ease of setup.

This change ensures users have the most up-to-date and streamlined information when setting up their development environment, keeping installations smooth and developer-friendly. 🚀