Remove explicit locale setting, it is managed by load_fullcalendar.html

AKPlan/templates/AKPlan/plan_detail.html

@@ -18,8 +18,6 @@
                     // Adapt to timezone of the connected event
                     timeZone: '{{ event.timezone }}',
                     initialView: 'timeGrid',
-                    // Adapt to user selected locale
-                    locale: '{{ LANGUAGE_CODE }}',
                     // No header, not buttons
                     headerToolbar: {
                         left: '',

AKPlan/templates/AKPlan/plan_index.html

@@ -22,8 +22,6 @@
                         right: 'resourceTimelineDay,resourceTimelineEvent'
                     },
                     themeSystem: 'bootstrap',
-                    // Adapt to user selected locale
-                    locale: '{{ LANGUAGE_CODE }}',
                     initialView: 'resourceTimelineEvent',
                     views: {
                         resourceTimelineDay: {