[NFC] Remove a cast rendered unnecessary by r321409

See https://reviews.llvm.org/rC321409 for additional context.

llvm-svn: 321410
diff --git a/clang/lib/Parse/ParseTemplate.cpp b/clang/lib/Parse/ParseTemplate.cpp
index 9d27cd3..56a16b9 100644
--- a/clang/lib/Parse/ParseTemplate.cpp
+++ b/clang/lib/Parse/ParseTemplate.cpp
@@ -375,7 +375,7 @@
     
     if (NamedDecl *TmpParam
           = ParseTemplateParameter(Depth, TemplateParams.size())) {
-      TemplateParams.push_back(dyn_cast<NamedDecl>(TmpParam));
+      TemplateParams.push_back(TmpParam);
     } else {
       // If we failed to parse a template parameter, skip until we find
       // a comma or closing brace.