Fix slot template prop naming

aleksis/apps/alsijil/frontend/components/coursebook/absences/ParticipationList.vue

@@ -18,7 +18,7 @@ import documentationPartMixin from "../documentation/documentationPartMixin";
           v-bind="$attrs"
           v-on="$listeners"
         >
-          <template :default="{ active }">
+          <template #default="{ active }">
             <v-list-item-action>
               <v-checkbox :input-value="active" />
             </v-list-item-action>