Use arrow functions everywhere for consistency

kfet/open/static/kfetopen/kfet-open.js

@@ -96,7 +96,7 @@ OpenKfet.prototype = {
         }).fail(function ($xhr) {
             switch ($xhr.status) {
                 case 403:
-                    requestAuth({ 'errors': {} }, this.toggle_force_close.bind(this));
+                    requestAuth({ 'errors': {} }, () => this.toggle_force_close);
                     break;
             }
         });