message: docs: fix typo comment
diff: @@ -19,7 +19,7 @@ it('schedules a 10-second timer after 1 second', () => {
  // (but not any new timers that get created during that process)
  jest.runOnlyPendingTimers();
  - // At this point, our 1-second timer should have fired it's callback
  + // At this point, our 1-second timer should have fired its callback
  expect(callback).toBeCalled();
  // And it should have created a new timer to start the game over in
  