gtkrevealer: fix preferred width calculation
gtkrevealer: fix preferred width calculation

A typo which was using minimum_width for natural_width and viceversa.

Adamovskiy/gtk,jadahl/gtk,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,grubersjoe/adwaita,grubersjoe/adwaita,Adamovskiy/gtk,Adamovskiy/gtk,jadahl/gtk,Adamovskiy/gtk,jigpu/gtk,alexlarsson/gtk,alexlarsson/gtk,chergert/gtk,davidgumberg/gtk,chergert/gtk,alexlarsson/gtk,chergert/gtk,alexlarsson/gtk,Adamovskiy/gtk,jigpu/gtk,davidgumberg/gtk,grubersjoe/adwaita,jigpu/gtk,chergert/gtk,alexlarsson/gtk,grubersjoe/adwaita,Adamovskiy/gtk,jadahl/gtk,Adamovskiy/gtk,jigpu/gtk,jigpu/gtk,grubersjoe/adwaita,davidgumberg/gtk,jigpu/gtk,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,davidgumberg/gtk,chergert/gtk,davidgumberg/gtk,jadahl/gtk,chergert/gtk,grubersjoe/adwaita,davidgumberg/gtk,grubersjoe/adwaita,grubersjoe/adwaita,jadahl/gtk,chergert/gtk,jadahl/gtk,alexlarsson/gtk,chergert/gtk,Adamovskiy/gtk,jigpu/gtk,jigpu/gtk