dillon1000/react

[Fizz] Should be considered complete inside onShellReady callback (#33295)

We decremented `allPendingTasks` after invoking `onShellReady`. Which
means that in that scope it wasn't considered fully complete.

Since the pattern for flushing in Node.js is to start piping in
`onShellReady` and that's how you can get sync behavior, this led us to
think that we had more work left to do. For example we emitted the
`writeShellTimeInstruction` in this scenario before.