[clang] [Clang] [C++26] Implement P2573R2: `= delete("should have a reason");` (PR #86526)

[Mariya Podchishchaeva via cfe-commits]

================
@@ -1936,6 +1936,9 @@ void TextNodeDumper::VisitFunctionDecl(const FunctionDecl *D) {
   if (D->isTrivial())
     OS << " trivial";
 
+  if (const auto *M = D->getDeletedMessage())
----------------
Fznamznon wrote:

Here too. 
```suggestion
  if (const StringLiteral *M = D->getDeletedMessage())
```

https://github.com/llvm/llvm-project/pull/86526