Auto merge of #130025 - Urgau:missing_docs-expect, r=petrochenkov

Also emit `missing_docs` lint with `--test` to fulfil expectations

This PR removes the "test harness" suppression of the `missing_docs` lint to be able to fulfil `#[expect]` (expectations) as it is now "relevant".

I think the goal was to maybe avoid false-positive while linting on public items under `#[cfg(test)]` but with effective visibility we should no longer have any false-positive.

Another possibility would be to query the lint level and only emit the lint if it's of expect level, but that is even more hacky.

Fixes rust-lang/rust#130021

try-job: x86_64-gnu-aux