Rollup merge of rust-lang#48761 - frewsxcv:frewsxcv-rm-python, r=alex…

…crichton

Remove seemingly unused sugarise-doc-comments Python script.

This Python script converts documentation comments from the
`#[doc = "..."]` attribute to the `///` syntax. It was added six
years ago, presumably to help with the transition when `///` was
implemented and hasn't really been touched since. I don't think there's
much value in keeping it around at this point.