message: Delete confusing async keyword
  Async is used is only used in one of two similar promise examples. It threw me off.
diff: @@ -66,7 +66,7 @@ Be sure to return the promise - if you omit this `return` statement, your test w
  If you expect a promise to be rejected use the `.catch` method. Make sure to add `expect.assertions` to verify that a certain number of assertions are called. Otherwise a fulfilled promise would not fail the test.
  ```js
  -test('the fetch fails with an error', async () => {
  +test('the fetch fails with an error', () => {
  expect.assertions(1);
  return fetchData().catch(e =>
  expect(e).toMatch('error')
  