Update list of US Letter locales
Update list of US Letter locales

Sync paper size fallbacks with the latest 1.8.1 CLDR table (#618000).

Unity-Technologies/gtk,Unity-Technologies/gtk,Unity-Technologies/gtk,johne53/MB3Gtk-2,johne53/MB3Gtk-2,Unity-Technologies/gtk,johne53/MB3Gtk-2,Distrotech/gtk,Distrotech/gtk,johne53/MB3Gtk-2,Distrotech/gtk,Unity-Technologies/gtk,johne53/MB3Gtk-2,Distrotech/gtk,Distrotech/gtk