Fix ScreenChooserDialog Layout
contentWidth and contentHeight of ScrollView must be set when more than one item is used. This was not needed before porting from Kirigami.CardsGridView to Kirigami.CardsLayout in ebfeb51f since CardsGridView was just one item.
Set Layout.preferredHeight of PipeWireDelegate so preview image has enough vertical space.
BUG: 479304 FIXED-IN: 6.0
(cherry picked from commit bab2ef4f)