Fix/improve social media bar

[kalenmike]

Some fixes to prevent the README showing up broken on PaperSpace.

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated social media logos and styling in README.

📊 Key Changes

• Replaced social media logos with new versions from 'ultralytics/assets' repository.
• Added style="text-decoration:none;" to remove underlines from hyperlinks.

🎯 Purpose & Impact

• Enhanced Visuals: Ensures a more polished and updated look for the project's README. 🖼️
• Improved Consistency: Normalizes styling across social media icons, making the presentation more cohesive. 🎨
• Better User Experience: Removing hyperlink underlines enhances readability and user experience on the project page. 👁️‍🗨️

[glenn-jocher]

@kalenmike thanks for the updates! I've pointed to the URLs to icons hosted at https://github.com/ultralytics/assets which work better for https://pypi.org/project/ultralytics/, and I've updated the Chinese docs also. I'll update ultralytics/hub so the next pypi release incorporates the new icon html.