gtkwindow: Fix the comment for an optimization
gtkwindow: Fix the comment for an optimization

The optimization was incorrect, and so it was changed in commit
2bf6824, but the comment to go along with it was never updated.

Adamovskiy/gtk,Lyude/gtk-,Adamovskiy/gtk,Adamovskiy/gtk,ahodesuka/gtk,jadahl/gtk,jessevdk/gtk,chergert/gtk,Lyude/gtk-,jadahl/gtk,chergert/gtk,jigpu/gtk,ahodesuka/gtk,jigpu/gtk,chergert/gtk,Lyude/gtk-,ahodesuka/gtk,jadahl/gtk,alexlarsson/gtk,Adamovskiy/gtk,jadahl/gtk,alexlarsson/gtk,grubersjoe/adwaita,grubersjoe/adwaita,davidgumberg/gtk,Adamovskiy/gtk,alexlarsson/gtk,jessevdk/gtk,jessevdk/gtk,Adamovskiy/gtk,alexlarsson/gtk,jigpu/gtk,davidgumberg/gtk,Lyude/gtk-,chergert/gtk,jigpu/gtk,jessevdk/gtk,jigpu/gtk,jigpu/gtk,alexlarsson/gtk,alexlarsson/gtk,jadahl/gtk,ahodesuka/gtk,ahodesuka/gtk,jessevdk/gtk,jadahl/gtk,jessevdk/gtk,chergert/gtk,alexlarsson/gtk,alexlarsson/gtk,davidgumberg/gtk,jigpu/gtk,grubersjoe/adwaita,chergert/gtk,davidgumberg/gtk,ahodesuka/gtk,grubersjoe/adwaita,grubersjoe/adwaita,ahodesuka/gtk,jigpu/gtk,davidgumberg/gtk,chergert/gtk,Lyude/gtk-,davidgumberg/gtk,grubersjoe/adwaita,jadahl/gtk,ahodesuka/gtk,Adamovskiy/gtk,davidgumberg/gtk,grubersjoe/adwaita,davidgumberg/gtk,jadahl/gtk,Lyude/gtk-,Adamovskiy/gtk,grubersjoe/adwaita,chergert/gtk,Lyude/gtk-,jessevdk/gtk,Lyude/gtk-