Reprocess CSS to be not minimised.

public/patterns/core/colours/index.html

@@ -291,7 +291,7 @@
             </sample-block>
           </color-sample>
         </color-samples>
-        <div class="tab-group" id="colors">
+        <tabset id="colors">
           <div data-tab="css">
             <pre class="language-css">:root {
 	--colour-blue: #2e51a1;
@@ -339,6 +339,6 @@
 	}
 }</pre>
           </div>
-        </div>
+        </tabset>
   </body>
 </html>