Fix select-timetable value prop type

Timetable.vue binds an object to select-timetable v-model.

aleksis/apps/chronos/frontend/components/SelectTimetable.vue

@@ -5,7 +5,7 @@ export default {
   name: "SelectTimetable",
   props: {
     value: {
-      type: String,
+      type: Object,
       required: false,
       default: null,
     },