Making some attribute diagnostics more consistent. Removes a newly-unused diagnostic.

Reviewed by Fariborz Jahanian

llvm-svn: 195578
diff --git a/clang/test/SemaObjC/arc-unavailable-for-weakref.m b/clang/test/SemaObjC/arc-unavailable-for-weakref.m
index eab5f2c..8274802 100644
--- a/clang/test/SemaObjC/arc-unavailable-for-weakref.m
+++ b/clang/test/SemaObjC/arc-unavailable-for-weakref.m
@@ -90,3 +90,5 @@
 __attribute__((objc_arc_weak_reference_unavailable(1)))	// expected-error {{'objc_arc_weak_reference_unavailable' attribute takes no arguments}}
 @interface I3
 @end
+
+int I4 __attribute__((objc_arc_weak_reference_unavailable)); // expected-error {{'objc_arc_weak_reference_unavailable' attribute only applies to Objective-C interfaces}}