chore(doc-gen): show arguments as a subsection of the usage section

Previously, on the docs of directives which include the `animation` section, `arguments` are shown as an `h3` element below the `animation` `h2` element, making it look like it's a subsection of `animations`.

This commit ensures that the àrgument` `h3`element is rendered correctly after the `usage` `h2` element.

Fixes angular#15645
Closes angular#15646

docs/config/templates/ngdoc/api/directive.template.html

@@ -61,12 +61,12 @@ <h2 id="usage">Usage</h2>
   </div>
   {% endblock -%}
 
+  {% include "lib/params.template.html" %}
+  {% include "lib/events.template.html" %}
+
   {%- if doc.animations %}
   <h2 id="animations">Animations</h2>
   {$ doc.animations | marked $}
   {$ 'module:ngAnimate.$animate' | link('Click here', doc) $} to learn more about the steps involved in the animation.
   {%- endif -%}
-
-  {% include "lib/params.template.html" %}
-  {% include "lib/events.template.html" %}
 {% endblock %}