Remove Sky tests that we don't intend to port to the new world

sky/tests/events/custom-event.sky

-<script>
-import "../resources/third_party/unittest/unittest.dart";
-import "../resources/unit.dart";
-
-import "dart:sky";
-
-class MyEvent extends Event {
-  MyEvent() : super(type: "awesome", bubbles: true);
-
-  bool get isCustom => true;
-}
-
-void main() {
-  initUnit();
-
-  test("should be able to dispatch", () {
-    var event = new MyEvent();
-    expect(event.isCustom, isTrue);
-    expect(event.type, equals("awesome"));
-    expect(event.bubbles, isTrue);
-    expect(event.cancelable, isFalse);
-    expect(event.isCustom, isTrue);
-
-    bool gotEvent = false;
-    var element = document.createElement("div");
-    element.addEventListener("awesome", (e) {
-      expect(e, equals(event));
-      expect(event.isCustom, isTrue);
-      gotEvent = true;
-    });
-    element.dispatchEvent(event);
-    expect(gotEvent, isTrue);
-  });
-}
-</script>