Rollup merge of #119600 - aDotInTheVoid:comment-fix, r=compiler-errors

Remove outdated references to librustc_middle

The relevant comment is now in https://github.com/rust-lang/rust/blob/791a53f380d5cf800191f25941c94ace5099876e/compiler/rustc_middle/src/tests.rs#L3-L13

Author: matthiaskrgr