gmessages: Clarify documentation for G_LOG_LEVEL_CRITICAL
gmessages: Clarify documentation for G_LOG_LEVEL_CRITICAL

Clarify that it’s a critical //warning//, not a critical something-else.

johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,MathieuDuponchelle/glib,endlessm/glib,Distrotech/glib,MathieuDuponchelle/glib,Distrotech/glib,MathieuDuponchelle/glib,Distrotech/glib,endlessm/glib,Distrotech/glib,Distrotech/glib,johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,MathieuDuponchelle/glib,endlessm/glib,MathieuDuponchelle/glib