chore: clean up Hugging Face Repos old files, future default branches

[gabrielle-ong]

Task list

• [ ] Delete old .gguf and metadata.yaml files from main branch
• [ ] Update default branches in metadata.yml for some models https://github.com/janhq/cortex.cpp/issues/1418#issuecomment-2392716451

Ongoing discussion:

• [ ] remove id from model.yml? #1410