[Test][Backtracing] Disable FatalError test temporarily.

Some CI nodes currently cause this test to fail because of outdated
software.  Disable it for now.

Author: al45tair

test/Backtracing/FatalError.swift

@@ -9,6 +9,7 @@
 // REQUIRES: executable_test
 // REQUIRES: backtracing
 // REQUIRES: OS=macosx || OS=linux-gnu
+// REQUIRES: rdar116790881
 
 func level1() {
   level2()