Complete doc migration
Reverts https://github.com/huggingface/transformers/pull/20125

Everything is handled on the doc-builder side now 😊
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20267). All of your documentation changes will be reflected on that endpoint.<|||||>LGTM, and thanks for the awesome work. I bag my courage to approve.
<|||||>well, I forgot to approve after leaving a comment, sorry.