The restorable Navigator methods incorrectly stated that they return a Future, e.g [1]:

Returns a Future that completes to the result value passed to pop when the pushed route is popped off the navigator.

The correct return value was documented a few lines below that:

The method returns an opaque ID for the pushed route that can be used by the RestorableRouteFuture to gain access to the actual Route object added to the navigator and its return value.

This change removes the incorrect docs for the restorable methods.

[1] https://api.flutter.dev/flutter/widgets/Navigator/restorablePush.html