Rollup merge of rust-lang#54311 - frewsxcv:frewsxcv-readme, r=GuillaumeGomez

Remove README with now-out-of-date docs about docs.

These docs haven't really been touched in years, and from what I tried, the `rustdoc` commands don't work. Seems like we don't need this?

Author: GuillaumeGomez