This re-enables the iOS Scenarios tests which have been flaky in the
last couple days.
Disabling two tests where we've seen the flakes:
* AppLifecycleTests testFlutterViewControllerDetachingSendsApplicationLifecycle
* FlutterViewControllerInitialRouteTest testSettingInitialRoute
This reverts commit 0c6c265a6f38bcacf551690a8fc8f78bb4f2c285.