[clang] [clang] fix serialization of SubstNonTypeTemplateParmExpr (PR #134560)

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eaeltsin wrote:

@mizvekov - can [this](https://github.com/llvm/llvm-project/pull/132401#issuecomment-2795078260) also be related, or it needs a separate investigation?

https://github.com/llvm/llvm-project/pull/134560