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 https://github.com/rust-lang/rust/issues/130021

try-job: x86_64-gnu-aux

compiler/rustc_lint/src/builtin.rs

@@ -426,12 +426,6 @@ impl MissingDoc {
         article: &'static str,
         desc: &'static str,
     ) {
-        // If we're building a test harness, then warning about
-        // documentation is probably not really relevant right now.
-        if cx.sess().opts.test {
-            return;
-        }
-
         // Only check publicly-visible items, using the result from the privacy pass.
         // It's an option so the crate root can also use this function (it doesn't
         // have a `NodeId`).