Convert all modifier constants to Gdk.ModifierType
Convert all modifier constants to Gdk.ModifierType

Signed-off-by: Manuel Quiñones <6f5069c5b6be23302a13accec56587944be09079@laptop.org>

GNOME/pygobject,choeger/pygobject-cmake,MathieuDuponchelle/pygobject,jdahlin/pygobject,davibe/pygobject,GNOME/pygobject,GNOME/pygobject,thiblahute/pygobject,davidmalcolm/pygobject,davidmalcolm/pygobject,davibe/pygobject,davibe/pygobject,jdahlin/pygobject,choeger/pygobject-cmake,choeger/pygobject-cmake,thiblahute/pygobject,pexip/pygobject,thiblahute/pygobject,pexip/pygobject,davidmalcolm/pygobject,davibe/pygobject,jdahlin/pygobject,sfeltman/pygobject,MathieuDuponchelle/pygobject,pexip/pygobject,MathieuDuponchelle/pygobject,sfeltman/pygobject,sfeltman/pygobject