message: refactor(forms): compile forms cleanly with TypeScript 2.4
diff: @@ -616,7 +616,7 @@ export function main() {
  it('should return true when the component is enabled', () => {
  expect(group.contains('required')).toEqual(true);
  - group.enable('optional');
  + group.enable();
  expect(group.contains('optional')).toEqual(true);
  });
  