Get rid of Google Tag Manager

We have migrated to plausible long ago

index.html

@@ -354,15 +354,6 @@ __      __   _  __   ____  __
 	}
 	loadCX();
     </script>
-<!-- Google tag (gtag.js) -->
-<script defer src="https://www.googletagmanager.com/gtag/js?id=G-818T3Y0PEY"></script>
-<script defer>
-  window.dataLayer = window.dataLayer || [];
-  function gtag(){dataLayer.push(arguments);}
-  gtag('js', new Date());
-
-  gtag('config', 'G-818T3Y0PEY');
-</script>
   </body>
 </html>