Revert "gobject-2.0: make ObjectClass.list_properties transfer container"
Revert "gobject-2.0: make ObjectClass.list_properties transfer container"

Breaks bootstrapping with valac <= 0.24

rvu95/vala,rvu95/vala,spidermonkdust/vala,spidermonkdust/vala,frida/vala,flobrosch/vala-fixes,GNOME/vala,frida/vala,rvu95/vala,GNOME/vala,spidermonkdust/vala,frida/vala,frida/vala,GNOME/vala,flobrosch/vala-fixes,GNOME/vala,flobrosch/vala-fixes,frida/vala