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.
{timeoutMs: 2000},
    );
    expect(Scheduler).toFlushAndYield(['Suspend! [B]', 'Loading...']);
    
    expect(ReactNoop.getChildren()).toEqual([span('A')]);
    Scheduler.unstable_advanceTime(500);
    await advanceTimers(500);
    
    expect(ReactNoop.getChildren()).toEqual([
      hiddenSpan('A'),
      span('Loading...'),
    ]);
    Scheduler.unstable_advanceTime(2000);
    await advanceTimers(2000);
    expect(Scheduler).toHaveYielded(['Promise resolved [B]']);
    expect(Scheduler).toFlushAndYield(['B']);
    expect(ReactNoop.getChildren()).toEqual([span('B')]);
    React.unstable_withSuspenseConfig(
      () => {
        
        React.unstable_withSuspenseConfig(() =>
          ReactNoop.render(<App page="B" unrelated={true} />),
        );
        
        
        Scheduler.unstable_next(() => ReactNoop.render(<App page="C" />));
      },
      {timeoutMs: 60000},
    );
    expect(Scheduler).toFlushAndYield(['B', 'Suspend! [C]', 'Loading...']);