Move from h4s and misc to h5s so headings from example snippets don't show in our table of contents

docs/4.0/content/reboot.md

@@ -342,7 +342,7 @@ HTML5 adds [a new global attribute named `[hidden]`](https://developer.mozilla.o
 {% endhighlight %}
 
 {% callout warning %}
-#### jQuery incompatibility
+##### jQuery incompatibility
 
 `[hidden]` is not compatible with jQuery's `$(...).hide()` and `$(...).show()` methods. Therefore, we don't currently especially endorse `[hidden]` over other techniques for managing the `display` of elements.
 {% endcallout %}