run eslint to fix most var instances

src/components/serviceworker/notifications.js

@@ -2,7 +2,7 @@
 (function () {
     'use strict';
 
-    var connectionManager;
+    let connectionManager;
 
     function getApiClient(serverId) {
         if (connectionManager) {
@@ -28,12 +28,12 @@
 
     /* eslint-disable-next-line no-restricted-globals -- self is valid in a serviceworker environment */
     self.addEventListener('notificationclick', function (event) {
-        var notification = event.notification;
+        const notification = event.notification;
         notification.close();
 
-        var data = notification.data;
-        var serverId = data.serverId;
-        var action = event.action;
+        const data = notification.data;
+        const serverId = data.serverId;
+        const action = event.action;
 
         if (!action) {
             clients.openWindow('/');