docs: use GA4 instead of UA

solara/website/templates/index.html.j2

@@ -13,26 +13,15 @@
     <link rel="stylesheet" href="/_solara/cdn/@docsearch/css@3/dist/style.css" />
     <script src="/_solara/cdn/@docsearch/js@3"></script>
 
-    <!-- Google Analytics -->
+    <!-- Google tag (gtag.js) -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id=G-G985FTLWGQ"></script>
     <script>
-    (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
-    (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
-    m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
-    })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
-    _solara_skip_use_ga = (window.location.hostname == 'localhost') || (window.location.hostname == '0.0.0.0');
-    if(!_solara_skip_use_ga) {
-        ga('create', 'UA-240047566-1', 'auto');
-        ga('send', 'pageview');
-    }
+    window.dataLayer = window.dataLayer || [];
+    function gtag(){dataLayer.push(arguments);}
+    gtag('js', new Date());
+
+    gtag('config', 'G-G985FTLWGQ');
     </script>
     <!-- End Google Analytics -->
     {{ super() }}
-    <script>
-    if(!_solara_skip_use_ga) {
-        // for client side routing
-        window.addEventListener('solara.router', function(event) {
-            ga('send', 'pageview', window.location.pathname);
-        });
-    }
-    </script>
 {% endblock %}