Add TF and TFLite models to .gitignore

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhanced model export support in YOLOv5 📦

📊 Key Changes

• Added *.pb to Git ignore for TensorFlow protobuf files
• Included *.tflite for TensorFlow Lite models
• Added *.h5 for Keras model files
• Ignored *_saved_model/ directories

🎯 Purpose & Impact

• Purpose: To ensure that various model file types and directories created during export processes are not accidentally committed to the repository.
• Impact: Developers will have a cleaner working directory, lowered risk of committing large model files, and an easier time managing code with support for popular machine learning formats. For users, this translates to more streamlined model conversion and deployment across different platforms.