textview: Fix cursor positioning oddities when scrolling through Pg Up/Down
textview: Fix cursor positioning oddities when scrolling through Pg Up/Down

Use the adjustment target value when repositioning the cursor, and remove the
checks that ensured the cursor was made onscreen immediately, as there will
be definitely a delay on animated adjustment changes.

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