[clang] [clang] Improve diagnostic on [[nodiscard]] attribute (PR #112521)

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@@ -3182,11 +3182,12 @@ class CallExpr : public Expr {
 
   /// Returns the WarnUnusedResultAttr that is either declared on the called
   /// function, or its return type declaration.
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Sirraide wrote:

The comment should be expanded to also explain what the `NamedDecl*` in the pair is supposed to be

https://github.com/llvm/llvm-project/pull/112521