Remove custom example plugin. (#25784)

docs/4.0/utilities/clearfix.md

@@ -30,9 +30,10 @@ Easily clear `float`s by adding `.clearfix` **to the parent element**. Can also
 
 The following example shows how the clearfix can be used. Without the clearfix the wrapping div would not span around the buttons which would cause a broken layout.
 
-{% example html %}
+{% capture example %}
 <div class="bg-info clearfix">
   <button type="button" class="btn btn-secondary float-left">Example Button floated left</button>
   <button type="button" class="btn btn-secondary float-right">Example Button floated right</button>
 </div>
-{% endexample %}
+{% endcapture %}
+{% include example.html content=example %}