Remove flatpickr polyfill

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

templates/partials/datetime-fix.html

@@ -1,34 +0,0 @@
-{% load static %}
-<script>
-function initDatetime() {
-    $('input[type=datetime-local]').not(':disabled').flatpickr({
-        dateFormat: 'Y-m-dTH:m',
-        enableTime: true,
-        allowInput: true,
-        altInput: true,
-        altFormat: "d/m/y H:m",
-    });
-}
-$(document).ready(function () {
-    function supportsDateTime() {
-        var input = document.createElement('input');
-        input.setAttribute('type','datetime-local');
-        return input.type !== "text";
-    }
-    //Firefox reports support for datetime-local without properly supporting it. Bah.
-    if(!supportsDateTime() || navigator.userAgent.toLowerCase().indexOf('firefox') > -1){
-        $('<link>')
-          .appendTo('head')
-          .attr({type : 'text/css', rel : 'stylesheet'})
-          .attr('href', '{% static "css/flatpickr.css" %}');
-        $.when(
-            $.getScript( '{% static "js/flatpickr.min.js" %}' ),
-            $.Deferred(function(deferred){
-                $(deferred.resolve);
-            })
-        ).done(function(){
-            initDatetime();
-        });
-    }
-});
-</script>