Remove broken links to s-JoL/Open-Llama

[CSRessel]

What does this PR do?

I noticed a broken link in the README, for the source code of the Open-Llama model. This looks like it matches the docs where there's been a warning added:

This model is in maintenance mode only, so we won't accept any new PRs changing its code.

To reduce confusion (and link rot!) this PR updates all references to that code, by clarifying that the original source was removed.

For the previous discussion on model deprecation, see: #24922

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• Was this discussed/approved via a Github issue or the forum? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

Potential reviewers might be @stevhliu or @MKhalusova since it's docs, or @amyeroberts who I've seen approve a lot of README edits today, or @sgugger has previously reviewed PR's related to Open-Llama.

[amyeroberts]

Nice tidy up - thanks!

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint.