[ticket/16944] Unify footer code and clean up code

PHPBB3-16944

phpBB/styles/prosilver/template/simple_footer.html

@@ -46,7 +46,7 @@
 <script src="{T_ASSETS_PATH}/javascript/core.js?assets_version={T_ASSETS_VERSION}"></script>
 <!-- INCLUDEJS forum_fn.js -->
 <!-- INCLUDEJS ajax.js -->
-<script src="https://code.iconify.design/1/1.0.0-rc7/iconify.min.js"></script>
+{% INCLUDEJS T_ASSETS_PATH ~ '/iconify/iconify.min.js' %}
 
 <!-- EVENT simple_footer_after -->
 {$ICONIFY_ICONS}