Update README.md

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Improved clarity and consistency of the YOLOv5 README documentation.

📊 Key Changes

• Added a note specifying that all checkpoints are trained for 300 epochs using default settings.
• Clarified metrics terminology with bold formatting (e.g., mAP, Speed, TTA) and modified accompanying descriptions.
• Removed outdated information regarding Test Time Augmentation (TTA) and autoaugmentation.
• Provided cleaner, more concise instructions on how to reproduce model accuracy (mAP) and speed benchmarks.

🎯 Purpose & Impact

• 🎓 Enhanced Understanding: Non-expert users will now find it easier to understand performance metrics and reproduction steps.
• 🔍 Consistency: By bolding key terms, users can more quickly scan and find important information.
• 🧹 Updated Information: Removes outdated details, ensuring users are working with the most current data.
• 🚀 Ease of Use: Simplified reproduction commands aim to make it straightforward for users to benchmark models on their own systems.