Remove flatpickr polyfill

Firefox now supports it natively...finally! Closes #475

RIGS/templates/event_checklist_form.html

@@ -20,8 +20,6 @@
     <script src="{% static 'js/autocompleter.js' %}"></script>
     <script src="{% static 'js/tooltip.js' %}"></script>
 
-    {% include 'partials/datetime-fix.html' %}
-
     <script>
     $(document).ready(function () {
         $('button[data-action=add]').on('click', function (event) {