trivial: Remove prototype with no method
trivial: Remove prototype with no method

mitya57/appstream-glib,ximion/appstream-glib,ximion/appstream-glib,hughsie/appstream-glib,ximion/appstream-glib,superm1/appstream-glib,ikeydoherty/appstream-glib,hughsie/appstream-glib,ikeydoherty/appstream-glib,hughsie/appstream-glib,mitya57/appstream-glib,superm1/appstream-glib