gtktreeview: Fix horizontal grid lines
gtktreeview: Fix horizontal grid lines

The clipping was wrong so it was not drawing grid lines
outside the visible area, which broke due to the pixel cache.

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