[clang] NFC: remove leftover from injected class name redecl (#155959)

The code being removed became non-functional when injected class names
were removed from the redecl chain in
470c454, but that commit didn't clean
the code base out of all the workarounds for that state of affairs.

Author: mizvekov

clang/include/clang/AST/ASTNodeTraverser.h

@@ -649,21 +649,8 @@ class ASTNodeTraverser
 
   template <typename SpecializationDecl>
   void dumpTemplateDeclSpecialization(const SpecializationDecl *D) {
-    for (const auto *RedeclWithBadType : D->redecls()) {
-      // FIXME: The redecls() range sometimes has elements of a less-specific
-      // type. (In particular, ClassTemplateSpecializationDecl::redecls() gives
-      // us TagDecls, and should give CXXRecordDecls).
-      auto *Redecl = dyn_cast<SpecializationDecl>(RedeclWithBadType);
-      if (!Redecl) {
-        // Found the injected-class-name for a class template. This will be
-        // dumped as part of its surrounding class so we don't need to dump it
-        // here.
-        assert(isa<CXXRecordDecl>(RedeclWithBadType) &&
-               "expected an injected-class-name");
-        continue;
-      }
-      Visit(Redecl);
-    }
+    for (const auto *Redecl : D->redecls())
+      Visit(cast<SpecializationDecl>(Redecl));
   }
 
   template <typename TemplateDecl>