Unable to hide screen icons as instructed

[KatieWoe]

For phetsims/qa#838, seen on Win 11 Chrome.
The element gravityAndOrbits.general.model.screens.isUserNavigatableProperty is given in the model as being able to hide screen icons in the nav bar. However, this element does not seem to exist. I suspect gravityAndOrbits.general.model.screens.isUserNavigableProperty should be the element instead.

[arouinfar]

Thanks @KatieWoe. I can take care of fixing this, but I'd like to wait and see how many issues require editing the PhET-iO Guide so I can group everything into one commit. Related issues #450 #452.

[zepumph]

@samreid and I are cruising through issues linked in the GAO rc, and fixed this guy. Ready for cherry pick.

[KatieWoe]

This is fixed in RC3