Update train.py

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Adjustment of Intersection over Union (IoU) threshold for model validation during training in the Ultralytics YOLOv5 repository.

📊 Key Changes

• IoU threshold changed from:
  • 0.7 to 0.65 for COCO dataset validation
  • 0.6 for non-COCO dataset validation remains the same

🎯 Purpose & Impact

• 🎯 Purpose: To fine-tune the IoU threshold parameter for better pycocotools performance during model validation, specifically for COCO dataset.
• 💥 Impact: Users may experience a more accurate assessment of model performance on COCO datasets, potentially leading to improved model fine-tuning and better generalization.