message: chore(retryWhen): add dtslint deprecation test
  related
diff: @@ -16,3 +16,7 @@ it('should enforce types', () => {
  it('should enforce types of the notifier', () => {
  const o = of(1, 2, 3).pipe(retryWhen(() => 8)); // $ExpectError
  });
  +
  +it('should be deprecated', () => {
  + const o = of(1, 2, 3).pipe(retryWhen(() => of(true))); // $ExpectDeprecation
  +});
  \ No newline at end of file
  