fix: Class attribute on GTM

Author: imtodor

_layouts/default.html

@@ -72,7 +72,7 @@
         {% endif %}
         <!-- Google Tag Manager -->
         {% if site.google_tag_manager %} {% assign gtm_id = site.google_tag_manager %} {% else %} {% assign gtm_id = 'GTM-6X92' %} {% endif %}
-        <script type="text/plain" className="optanon-category-1">(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
+        <script type="text/plain" class="optanon-category-1">(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
         new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
         j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
         'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);