GtkStack: Remove gtk_widget_set_opacity call
GtkStack: Remove gtk_widget_set_opacity call

The corresponding call with 0.999 opacity is gone, so we don't need to
reset the opacity anymore.

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