chore: remove unused theme stylesheet reference from head.html

Author: JackGilmore

_includes/head.html

@@ -19,11 +19,6 @@
 
 
   <link rel="stylesheet" href="{{ "/assets/scripts/dist/vendor.css" | relative_url | append: cacheBust }}">
-  {% assign theme_name = site.jkan_theme | default: 'Default' %}
-  {% assign theme = site.data.themes | where:'name', theme_name | first %}
-  {% if theme and theme.src and theme.src != empty %}
-  <link rel="stylesheet" href="{{ theme.src }}">
-  {% endif %}
   <link rel="stylesheet" href="{{ "/assets/css/main.css" | relative_url | append: cacheBust }}">
   <link rel="canonical" href="{{ page.url | replace:'index.html','' | prepend: site.baseurl | prepend: site.url }}">
   <link rel="me" href="https://mastodon.scot/@opendatascotland">