Fix translucency of RoomScreen navigation bar.

[pixlwave]

Currently the screen uses a translucent bar but doesn't have any content beneath it. This needs more work as the obvious idea of telling the scrollview to ignore the top safe area reveals some text during the push animation:

Simulator.Screen.Recording.-.iPhone.14.-.2023-02-13.at.16.57.34.mp4

And removing the fixed .toolbarBackground(.visible, for: .navigationBar) modifier on the screen in combination with the ignoring the top safe area results in a completely missing navigation bar:

Simulator.Screen.Recording.-.iPhone.14.-.2023-02-13.at.17.22.47.mp4

The fix may involve messing with which component provides the view's the background colour.

[pixlwave]

Fixed by #1392.