Disable the test until rdar://31286125 is fixed.

Author: swiftix

test/Prototypes/CollectionTransformers.swift

@@ -12,7 +12,7 @@
 // RUN: %target-run-stdlib-swift
 // REQUIRES: executable_test
 // Remove XFAIL once rdar://31286125 is resolved.
-// XFAIL: *
+// REQUIRES: rdar31286125
 
 // FIXME: This test runs very slowly on watchOS.
 // UNSUPPORTED: OS=watchos