Repro case with a master build: https://codesandbox.io/s/stoic-mcnulty-dhygf?file=/src/App.js:668-703

Expected: we see content after a second.
Actual: fallback never resolves.

This happens in a sequence of:

1. Normal update
   - which suspends
2. Idle update
   - which also suspends
3. An unrelated normal update immediately followed by a ping (so they're batched)
   - here, we decide to stay on fallback, but should've shown the content

If you remove `_setVersion(v => v + 1);` on line 44 then the issue goes away.
expect(ReactNoop.getChildren()).toEqual([
      span('Loading A...'),
      span('Loading B...'),
    ]);
    
    
    
    ReactNoop.expire(5000);
    await advanceTimers(5000);
    expect(Scheduler).toHaveYielded(['Promise resolved [A]']);
    expect(Scheduler).toFlushAndYield(['A']);
    expect(ReactNoop.getChildren()).toEqual([span('A'), span('Loading B...')]);
    
    
    ReactNoop.expire(1000);
    await advanceTimers(1000);
    expect(Scheduler).toHaveYielded(['Promise resolved [B]']);
    expect(Scheduler).toFlushAndYield(['B']);
    expect(ReactNoop.getChildren()).toEqual([span('A'), span('B')]);
  });
  it('continues rendering siblings after suspending', async () => {
    
    ReactNoop.render(<Suspense fallback={<Text text="Loading..." />} />);
    expect(Scheduler).toFlushAndYield([]);
    
    ReactNoop.render(
      <Suspense fallback={<Text text="Loading..." />}>
        <Text text="A" />
        <AsyncText text="B" />
        <Text text="C" />