Update Ultralytics YouTube URL

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Update YouTube links to include subscription prompt in YOLOv3 READMEs.

📊 Key Changes

• YouTube links in the README files (English and Chinese versions) have been modified to include ?sub_confirmation=1, prompting users to subscribe to Ultralytics YouTube channel upon clicking.

🎯 Purpose & Impact

• Enhanced User Engagement: This makes it easier for visitors to subscribe to the YouTube channel, potentially increasing subscriber numbers and engagement. 📈
• Seamless Experience: Users can now subscribe to the YouTube channel in just one click without searching for the subscribe button, offering a smoother and more intuitive user experience. 👍
• Wider Reach: By simplifying the subscription process, the change may help Ultralytics's educational and informative content reach a wider audience, benefiting more users. 🌍