Fix freq property type
Fix freq property type

The `freq` property in `RRuleInputObject` was incorrectly typed as the `until` property of `RRuleOptions`, not `freq`.
fullcalendar/fullcalendar,fullcalendar/fullcalendar,arshaw/fullcalendar,arshaw/fullcalendar,fullcalendar/fullcalendar,arshaw/fullcalendar,fullcalendar/fullcalendar,arshaw/fullcalendar