[flake][buildcop] Disable vmo_test from dart-zircon-test

This is repeatedly flaking in CQ.
FLK-221 #progress

Change-Id: Ie0ef6dcac3a4a715d595f53a9af2afc2e2c67839
diff --git a/public/dart-pkg/zircon/test/vmo_test.dart b/public/dart-pkg/zircon/test/vmo_test.dart
index ab48ef4..f62d52a 100644
--- a/public/dart-pkg/zircon/test/vmo_test.dart
+++ b/public/dart-pkg/zircon/test/vmo_test.dart
@@ -23,7 +23,7 @@
       Uint8List fileData = fileVmo.map();
       String fileString = utf8.decode(fileData.sublist(0, fileVmo.size));
       expect(fileString, equals(fuchsia));
-    });
+    }, skip: 'FLK-221');
 
     test('duplicate', () {
       const String fuchsia = 'Fuchsia';