trivial: Fix up a typo when validating AppData files
trivial: Fix up a typo when validating AppData files

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