Use `hf_transfer` for faster downloading of preprocessing models

[okaris]

https://github.com/huggingface/hf_transfer

Just needs two lines of code

1. - "hf_transfer" to cog.yaml python_packages
2. os.environ["HF_HUB_ENABLE_HF_TRANSFER"] = "1" to the top of train.py and/or predict.py