fix untranslated validation message on course grader LEARNER-2450

cms/static/js/models/settings/course_grader.js

@@ -24,7 +24,7 @@ define(['backbone', 'underscore', 'gettext'], function(Backbone, _, gettext) {
             var errors = {};
             if (_.has(attrs, 'type')) {
                 if (_.isEmpty(attrs['type'])) {
-                    errors.type = 'The assignment type must have a name.';
+                    errors.type = gettext('The assignment type must have a name.');
                 }
                 else {
                 // FIXME somehow this.collection is unbound sometimes. I can't track down when