Chganged approverUsers methods to use axios

app/assets/javascripts/api.js

@@ -182,14 +182,16 @@ const Api = {
 
   approverUsers(search, options, callback = $.noop) {
     const url = Api.buildUrl('/autocomplete/users.json');
-    return $.ajax({
-      url,
-      data: $.extend({
+    return axios.get(url, {
+      params: Object.assign({
         search,
         per_page: 20,
       }, options),
-      dataType: 'json',
-    }).done(callback);
+    }).then(({ data }) => {
+      callback(data);
+
+      return data;
+    });
   },
 
   ldap_groups(query, provider, callback) {

ee/app/assets/javascripts/approvers_select.js

@@ -79,9 +79,9 @@ export default class ApproversSelect {
       query: (query) => {
         const fetchGroups = this.fetchGroups(query.term);
         const fetchUsers = this.fetchUsers(query.term);
-        return $.when(fetchGroups, fetchUsers).then((groups, users) => {
+        return Promise.all([fetchGroups, fetchUsers]).then(([groups, users]) => {
           const data = {
-            results: groups[0].concat(users[0]),
+            results: groups.concat(users),
           };
           return query.callback(data);
         });