Update Dockerfile

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhanced Docker setup with distributed data parallel (DDP) testing support. 🐋🔧

📊 Key Changes

• Included a new commented-out section for distributed data parallel (DDP) testing using PyTorch in the Dockerfile.

🎯 Purpose & Impact

• Purpose: This change adds a command template for testing DDP within Docker, which is a way to train models across multiple GPUs, potentially speeding up training times and improving efficiency. 🏎️💨
• Potential Impact: While the command is commented out and not executed by default, it serves as a useful reference for developers who want to run DDP in the Ultralytics Docker environment. Users with access to multi-GPU setups could leverage this for more efficient training. ⚙️🚀