Search for the macro "view_mixed_html", I'm not sure if your app type uses this one but it will be easy to know.
Edit the macro and remove the .topics_action_link line. It will be like this:
<override_macro name="view_mixed_html">
<n.app_html>
<head>
<n.app_title/>
<n.mixed_table_stylesheet/>
</head>
<body>
<n.new_topic_action_link/>
<n.people_action_link/>
<n.options_action_menu/>
<n.mixed_table.mixed_table_columns />
<n.forum_footer/>
</body>
</n.app_html>
</override_macro>