[ODRHash] Remove debugging code from r305361

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@305362 91177308-0d34-0410-b5e6-96231b3b80d8

lib/AST/ODRHash.cpp

@@ -159,7 +159,6 @@ void ODRHash::AddTemplateArgument(TemplateArgument TA) {
       AddStmt(TA.getAsExpr());
       break;
     case TemplateArgument::Pack:
-      llvm_unreachable("Pack");
       break;
   }
 }