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.
React.unstable_withSuspenseConfig(
      () => ReactNoop.render(<App page="B" />),
      {timeoutMs: 2000},
    );
    expect(Scheduler).toFlushAndYield(['Hi!', 'Suspend! [B]', 'Loading B...']);
    
    expect(ReactNoop.getChildren()).toEqual([span('Hi!'), span('A')]);
    Scheduler.unstable_advanceTime(1800);
    await advanceTimers(1800);
    expect(Scheduler).toFlushAndYield([]);
    
    expect(ReactNoop.getChildren()).toEqual([span('Hi!'), span('A')]);
    Scheduler.unstable_advanceTime(1500);
    await advanceTimers(1500);
    expect(Scheduler).toHaveYielded(['Promise resolved [B]']);
    expect(ReactNoop.getChildren()).toEqual([
      span('Hi!'),
      span('Loading B...'),
    ]);
  });
  
  it('supports delaying a busy spinner from disappearing', async () => {
    const SUSPENSE_CONFIG = {
      timeoutMs: 10000,
      busyDelayMs: 500,
      busyMinDurationMs: 400,
    };
    let transitionToPage;
    function App() {