[clang] [clang] apply clang-tidy's llvm-redundant-casting (NFC) (PR #191322)

[Timm Baeder via cfe-commits]

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@@ -444,7 +444,7 @@ bool CheckConstant(InterpState &S, CodePtr OpPC, const Descriptor *Desc) {
   // If we're evaluating the initializer for a constexpr variable in C23, we may
   // only read other contexpr variables. Abort here since this one isn't
   // constexpr.
-  if (const auto *VD = dyn_cast_if_present<VarDecl>(S.EvaluatingDecl);
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tbaederr wrote:

To match the coding style, the `auto` should use the type instead after removing the cast.

https://github.com/llvm/llvm-project/pull/191322