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

[gabrielle-ong]

Task list

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

Ongoing discussion:

• [x] remove id from model.yml? janhq/cortex.cpp#1410

[hahuyhoang411]

Finished remove all of the gguf files in main branch

[gabrielle-ong]

Thank you so much @hahuyhoang411 <3