qml: remove bad model aliases

It does not seem possible to make model read-only, so the best would be to not use aliases here. If we can not make model property read-only, this leads to a dangerous situation of the model being changed accidentally or for other reasons which would be very hard to debug.

If we overload the model as read-only, base class still does not use the override. Since there is ListSelectionModel in the base class, it will continue to be bound to the old model instead of the new set one.