Use Hugo's Chroma highlighter rather than Highlight.js

Hugo has built in support for build time highlighting via Chroma. The
Beautiful Hugo theme is also enabling Highlight.js. Disable Highlight.js
so that we can gain control over the highlighting from the site config.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

themes/beautifulhugo/layouts/partials/footer.html

@@ -85,8 +85,6 @@
 <script src="{{ "js/search.js" | absURL }}"></script>
 <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
 <script src="{{ "js/main.js" | absURL }}"></script>
-<script src="{{ "js/highlight.min.js" | absURL }}"></script>
-<script> hljs.initHighlightingOnLoad(); </script>
 <script> renderMathInElement(document.body); </script>
 <!-- Load PhotoSwipe js if the load-photoswipe shortcode has been used -->
 {{ if ($.Scratch.Get "photoswipeloaded") }}