[simple] link preferences on /about and /stats

We want to link the preferences from every page
(except of course the preferences page).

searx/templates/simple/preferences.html

@@ -94,6 +94,7 @@
 {%- endmacro -%}
 
 {% block head %} {% endblock %}
+{% block linkto_preferences %}{% endblock %}
 {% block content %}
 <h1>{{ _('Preferences') }}</h1>