Update nav.html

Changed `site.html_pages` to `pages_list`, to repeat the nav order of the grandchildren in the nav panel.

_includes/nav.html

@@ -29,7 +29,7 @@
                     {%- endif -%}
                     <a href="{{ child.url | absolute_url }}" class="navigation-list-link{% if page.url == child.url %} active{% endif %}">{{ child.title }}</a>
                     {%- if child.has_children -%}
-                        {%- assign grand_children_list = site.html_pages | where: "parent", child.title | where: "grand_parent", node.title -%}
+                        {%- assign grand_children_list = pages_list | where: "parent", child.title | where: "grand_parent", node.title -%}
                         <ul class="navigation-list-child-list">
                         {%- for grand_child in grand_children_list -%}
                           <li class="navigation-list-item {% if page.url == grand_child.url %} active{% endif %}">