How to Hide the "Flamingo auto trash" Admin Menu

function plt_hide_inazo_flamingo_automatically_delete_old_messages_menus() {
	//Hide the "Settings → Flamingo auto trash" menu.
	remove_submenu_page('options-general.php', 'inazo.flamingo.auto.trash.config');
}

add_action('admin_menu', 'plt_hide_inazo_flamingo_automatically_delete_old_messages_menus', 11);

Where do I put this code?