[bnb] Move documentation
# What does this PR do?


- move bnb documentation to `perf_infer_gpu_many.mdx` as it was previously set to `perf_train_gpu_one.mdx` which is not relevant in the case of `bitsandbytes` integration since it supports inference only.

cc @stas00

I do have a question though, what about `perf_infer_gpu_one.mdx`? I think that the `bnb` documentation could fit well in this file as well since it supports single GPU inference too.
_The documentation is not available anymore as the PR was closed or merged._<|||||>yeah, I wasn't sure, probably you're right and then like  perf_train_gpu_many.mdx says on top to first read perf_train_gpu_one.mdx - add the same to perf_infer_gpu_many.mdx?<|||||>Yep makes sense! I propose a small refactoring at 2018285dd60c34d2654b0c51e523d7b1e815b989 !
Let me know if this works for you <|||||>The proposed change would be difficult to maintain and 2 copies will get out of sync. Only one copy please - if you prefer the one gpu doc that's where it should be. the other one linking to it.<|||||>Proposed a change in 5f8a3aeb035e8b086d0f9045550000b6be0fb630 ! Let me know if this works for you <|||||>Thanks a lot @stas00 for iterating on the changes 💪 