Prune an unused diagnostic, detected after improving the script in r172330

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172331 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticSemaKinds.td

@@ -4323,8 +4323,6 @@ def error_no_super_class_message : Error<
   "no @interface declaration found in class messaging of %0">;
 def error_root_class_cannot_use_super : Error<
   "%0 cannot use 'super' because it is a root class">;
-def err_invalid_receiver_to_message : Error<
-  "invalid receiver to message expression">;
 def err_invalid_receiver_to_message_super : Error<
   "'super' is only valid in a method body">;
 def err_invalid_receiver_class_message : Error<