Stop preloading tracking scripts. They mess with the loading order an…

…d slow page rendering down

docs/_includes/default.html

@@ -10,12 +10,6 @@
       as="image"
       crossorigin="anonymous"
     />
-    <link
-      rel="prefetch"
-      href="https://www.google-analytics.com/analytics.js"
-      crossorigin="anonymous"
-    />
-    <link rel="preconnect" href="https://stats.g.doubleclick.net" />
     <link rel="stylesheet" href="css/normalize.css" />
     <link rel="stylesheet" href="css/style.css" />
     <link rel="stylesheet" href="css/prism.css" />