Rollup merge of #129544 - mu001999-contrib:dead-code/clean, r=compiler-errors

Removes dead code from the compiler

Detected by #128637

compiler/rustc_passes/messages.ftl

@@ -481,10 +481,6 @@ passes_must_not_suspend =
     `must_not_suspend` attribute should be applied to a struct, enum, union, or trait
     .label = is not a struct, enum, union, or trait
 
-passes_must_use_async =
-    `must_use` attribute on `async` functions applies to the anonymous `Future` returned by the function, not the value within
-    .label = this attribute does nothing, the `Future`s returned by async functions are already `must_use`
-
 passes_must_use_no_effect =
     `#[must_use]` has no effect when applied to {$article} {$target}
 

compiler/rustc_passes/src/errors.rs

@@ -371,13 +371,6 @@ pub struct FfiConstInvalidTarget {
     pub attr_span: Span,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(passes_must_use_async)]
-pub struct MustUseAsync {
-    #[label]
-    pub span: Span,
-}
-
 #[derive(LintDiagnostic)]
 #[diag(passes_must_use_no_effect)]
 pub struct MustUseNoEffect {