update holder.js image dimensions for sizing example

* update holder.js image dimensions for sizing example
  * use `100%` instead of `100%`
  *  https://github.com/imsky/holder#fluid-placeholders

site/docs/4.1/utilities/sizing.md

@@ -31,7 +31,7 @@ Width and height utilities are generated from the `$sizes` Sass map in `_variabl
 You can also use `max-width: 100%;` and `max-height: 100%;` utilities as needed.
 
 {% capture example %}
-<img class="mw-100" data-src="holder.js/1000px100?text=Max-width%20%3D%20100%25" alt="Max-width 100%">
+<img class="mw-100" data-src="holder.js/100px100?text=Max-width%20%3D%20100%25" alt="Max-width 100%">
 {% endcapture %}
 {% include example.html content=example %}