Fix PyPI badge URL

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Improved automated checks and updated branding links in the ultralytics/thop GitHub repository.

📊 Key Changes

• Activated broken link checks in GitHub workflows. 🔗
• Corrected the PyPI badge link for accurate project version display. 🏷️
• Updated social media and external links from PyTorch to Ultralytics. 🔄

🎯 Purpose & Impact

• Broken link checks ensure all URLs in the project are valid, enhancing the repository's reliability.
• Corrected PyPI badge provides users with up-to-date information about the latest version of ultralytics/thop, improving usability.
• Updated links reflect the shift in branding from PyTorch to Ultralytics, making it easier for users to find Ultralytics-related resources and social media, thereby strengthening the brand presence and community engagement. 🌐🤝