TensorBoard add_graph() fix

[glenn-jocher]

Possible fix for #3235

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Improved TensorBoard graph logging in YOLOv5 training routine.

📊 Key Changes

• Uncommented code for TensorBoard graph logging.
• Adjusted the position of TensorBoard image logging comment (code itself is not changed; just the comment position).

🎯 Purpose & Impact

• 🚀 Purpose: The uncommented lines enable the visualization of the model's computational graph in TensorBoard, which can help in debugging and understanding the model architecture.
• 🛠 Impact: Users who utilize TensorBoard for monitoring and analyzing model performance will now have easier access to visual representations of the model's graph without having to modify the code themselves. However, this could also mean slightly increased resource usage during training due to graph logging.

[glenn-jocher]

This PR will run the TensorBoard add_graph() method for all training runs now, so model architecture is viewable in the 'GRAPHS' section.