Update accessible.html

Added forgotten closing tag.

src/_includes/examples/accessible.html

@@ -75,7 +75,7 @@
 {% endhighlight %}
 
 {% highlight html %}
-<i class="fa fa-refresh fa-spin fa-3x fa-fw" aria-hidden="true"</i>
+<i class="fa fa-refresh fa-spin fa-3x fa-fw" aria-hidden="true"></i>
 <span class="sr-only">Refreshing...</span>
 
 <i class="fa fa-cog fa-spin fa-3x fa-fw" aria-hidden="true"></i>