Update files structure in 4. Sharing models and tokenizers - Sharing pretrained models

[sergiopaniego]

In the 4. Sharing models and tokenizers - Sharing pretrained models, there are some outdated references regarding the files structure from working with a .pt model.

In particular, there are a few mentions of pytorch_model.bin and some outdated references which are now model.safetensors.

This affects some git related content on the unit

[sergiopaniego]

This unit would also benefit from an in-depth review since for example the Repository class is deprecated: https://huggingface.co/docs/huggingface_hub/package_reference/repository#