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(Scheduler).toFlushAndYield(['A', 'B']);
    expect(ReactNoop.getChildren()).toEqual([span('A'), span('B')]);
    
    ReactNoop.render(<Foo showC={true} />);
    expect(Scheduler).toFlushAndYield([
      'Foo',
      'A',
      'Suspend! [C]',
      'Updating...',
      'B',
    ]);
    
    Scheduler.unstable_advanceTime(600);
    await advanceTimers(600);
    
    
    expect(ReactNoop.getChildren()).toEqual([
      hiddenSpan('A'),
      span('Updating...'),
      span('B'),
    ]);
    
    Scheduler.unstable_advanceTime(5000);
    await advanceTimers(5000);
    expect(Scheduler).toHaveYielded(['Promise resolved [C]']);
    expect(Scheduler).toFlushAndYield(['A', 'C']);
    expect(ReactNoop.getChildren()).toEqual([span('A'), span('C'), span('B')]);
  });
  it('favors showing the inner fallback for nested top level avoided fallback', async () => {
    function Foo({showB}) {