.text-hide docs: trivial indentation fix

docs/_includes/css/helpers.html

@@ -199,7 +199,7 @@
 {% highlight html %}
 <h1 class="text-hide">Custom heading</h1>
 {% endhighlight %}
-  {% highlight scss %}
+{% highlight scss %}
 // Usage as a Mixin
 .heading {
   .text-hide();