Explicitly convert artifact path to posix_path

[AyushExel]

This explicit check converts forward slashes in WindowsPath to back splashes supported by artifacts

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Improved Weights & Biases (W&B) dataset artifact handling in Ultralytics YOLOv5.

📊 Key Changes

• Modified the download_dataset_artifact method in the wandb_utils.py file.
• Dataset artifacts are now managed using the Path library.

🎯 Purpose & Impact

• 🔄 The change ensures better path management and compatibility across different operating systems.
• 🛠 Fixes potential issues with incorrect path formatting when downloading dataset artifacts from W&B.
• 🤝 Users should experience a more reliable and seamless integration with W&B for tracking and sharing datasets.

[glenn-jocher]

@AyushExel looks good, but it looks like .as_posix() is already returning a string, so the str() may be redundant?
https://docs.python.org/3/library/pathlib.html#pathlib.PurePath.as_posix

[AyushExel]

@glenn-jocher ahh yes.. Nice catch. Removed it