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

docs/4.0/content/images.md

@@ -19,7 +19,7 @@ Images in Bootstrap are made responsive with `.img-fluid`. `max-width: 100%;` an
 {% endhighlight %}
 
 {% callout warning %}
-#### SVG images and IE 10
+##### SVG images and IE 10
 
 In Internet Explorer 10, SVG images with `.img-fluid` are disproportionately sized. To fix this, add `width: 100% \9;` where necessary. This fix improperly sizes other image formats, so Bootstrap doesn't apply it automatically.
 {% endcallout %}

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 %}