.phpdoc/template: Add parent's meta description

It's not used for now but in case of

Author: adriendupuis

tools/php_api_ref/.phpdoc/template/class.html.twig

@@ -3,6 +3,7 @@
 {% block title %}{{ node.name }} | {{ parent() }}{% endblock %}
 {% block meta %}
     <meta name="description" content="{{ node.summary }}" />
+    {{ parent() }}
 {% endblock %}
 
 {% block content %}

tools/php_api_ref/.phpdoc/template/interface.html.twig

@@ -3,6 +3,7 @@
 {% block title %}{{ node.name }} | {{ parent() }}{% endblock %}
 {% block meta %}
     <meta name="description" content="{{ node.summary }}" />
+    {{ parent() }}
 {% endblock %}
 
 {% block content %}