Avoid an unnecessary GraphQL query

Ensures that the initial sort parameter is consistent with what's
computed on user interactions. This ensures that we don't unnecessarily
re-trigger a GraphQL mutation when sorting by creation date, descending.

app/assets/javascripts/incidents/components/incidents_list.vue

@@ -174,7 +174,7 @@ export default {
       redirecting: false,
       incidents: {},
       incidentsCount: {},
-      sort: 'created_desc',
+      sort: 'CREATED_DESC',
       sortBy: 'createdAt',
       sortDesc: true,
       statusFilter: '',