[docs] refactor copy-snippets syntax highlighting

Author: addyosmani

site/src/_includes/components/copy-snippet.njk

@@ -1,19 +1,17 @@
 {% extends "layouts/normal-section-wrapper.njk" %}
 {% block section %}
 <div class="copy-snippet-widget">
-  <div class="secondary-font-color"><strong>Place this snippet in your head or just before your close body tag:<strong></div>
+  <div class="tertiary-font-color"><strong>Place this snippet in your head or just before your close body tag:<strong></div>
 
   <div class="snippet-for-copy">
-  {% markdownConvert %}
-  ```html
-  <script src="https://cdnjs.cloudflare.com/ajax/libs/quicklink/{{ site.quicklinkVersion }}/quicklink.umd.js"></script>
-  <script>
-  window.addEventListener('load', () => {
-    quicklink.listen();
-  });
-  </script>
-  ```
-  {% endmarkdownConvert %}
+  {% highlight "html" %}
+<script src="https://cdnjs.cloudflare.com/ajax/libs/quicklink/{{ site.quicklinkVersion }}/quicklink.umd.js"></script>
+<script>
+window.addEventListener('load', () => {
+  quicklink.listen();
+});
+</script>
+  {% endhighlight %}
   </div>
 
   <div>