How to Hide the "Duplicate Tag Removal" Admin Menu

function plt_hide_free_duplicate_tag_removal_menus() {
	//Hide the "Settings → Duplicate Tag Removal" menu.
	remove_submenu_page('options-general.php', 'fdtr');
}

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

Where do I put this code?