web: Fix deprecation warning

web/index.html

@@ -33,10 +33,6 @@
   <link rel="manifest" href="manifest.json">
   <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/ua-parser.min.js"></script>
 
-  <script>
-    // The value below is injected by flutter build, do not touch.
-    var serviceWorkerVersion = null;
-  </script>
   <!-- This script adds the flutter initialization JS code -->
   <script src="flutter.js" defer></script>
 </head>
@@ -44,9 +40,9 @@
   <script>
     window.addEventListener('load', function(ev) {
       // Download main.dart.js
-      _flutter.loader.loadEntrypoint({
-        serviceWorker: {
-          serviceWorkerVersion: serviceWorkerVersion,
+      _flutter.loader.load({
+        serviceWorkerSettings: {
+          serviceWorkerVersion: {{flutter_service_worker_version}},
         },
         onEntrypointLoaded: function(engineInitializer) {
           engineInitializer.initializeEngine().then(function(appRunner) {