docs: Replace unsupported `facebookresearch/bitsandbytes`
# What does this PR do?

* Replace unsupported https://github.com/facebookresearch/bitsandbytes with https://github.com/TimDettmers/bitsandbytes, which is by the same author and still being maintained and updated. For reference, the latter repository is the one mentioned in your blog post https://huggingface.co/blog/hf-bitsandbytes-integration, which was co-written by Tim Dettmers.


## Before submitting
- [x] This PR fixes a typo or improves the docs

## Who can review?

Documentation: @sgugger
@TimDettmers

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- Tom Aarsen
_The documentation is not available anymore as the PR was closed or merged._