[Test] Fully disabled test.

It's failing on more platforms than originally thought.

rdar://107052715

Author: nate-chandler

test/ModuleInterface/actor_availability.swift

@@ -8,7 +8,7 @@
 // REQUIRES: VENDOR=apple
 
 // FIXME: rdar://107052715 temporarily disabled the test; fails on ios simulator
-// UNSUPPORTED: OS=ios
+// REQUIRES: rdar107052715
 
 // CHECK: #if compiler(>=5.3) && $Actors
 // CHECK-NEXT: public actor ActorWithImplicitAvailability {