[clang] [clang] fix matching of nested template template parameters (PR #130447)

[via cfe-commits]

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@@ -11363,14 +11363,17 @@ class Sema final : public SemaBase {
 
   /// The context in which we are checking a template parameter list.
   enum TemplateParamListContext {
-    TPC_ClassTemplate,
-    TPC_VarTemplate,
+    // For this context, Class, Variable, TypeAlias, and non-pack Template
+    // Template
+    // Parameters are the same.
+    TPC_Normal,
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cor3ntin wrote:

"Normal" doesn't make sense to me. I believe that we are better off just adding 
`TPC_TemplateTemplateParameterPack` and keeping everything else the same (even though _today_ these contexts are not differentiated anywhere)

https://github.com/llvm/llvm-project/pull/130447