refactor: remove gtag

Author: mrholek

src/pug/_partials/head.pug

@@ -35,14 +35,3 @@ link(href='css/examples.css', rel='stylesheet')
 
 script(src='js/config.js')
 script(src='js/color-modes.js')
-
-// Global site tag (gtag.js) - Google Analytics
-script(async='', src='https://www.googletagmanager.com/gtag/js?id=UA-118965717-3')
-script.
-  window.dataLayer = window.dataLayer || [];
-  function gtag(){dataLayer.push(arguments);}
-  gtag('js', new Date());
-  // Shared ID
-  gtag('config', 'UA-118965717-3');
-  // Bootstrap ID
-  gtag('config', 'UA-118965717-5');