deprecate OctoAI

[IgorKasianenko]

What does this PR do?

Fixes non existing API provider references

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• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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Thanks for contributing 🎉!

[Monireh2]

Thanks @IgorKasianenko for the PR. LGTM!
Please just remove the OctoAI from readme and keep other contents about RAG chatbot in the end-to-end-use-cases/README.md:

RAG Chatbot Example (running locally )

A complete example of how to build a Llama 3 chatbot hosted on your browser that can answer questions based on your own data using retrieval augmented generation (RAG). You can run Llama2 locally if you have a good enough GPU.