How to Hide the "Safe Redirect Manager" Admin Menu

function plt_hide_safe_redirect_manager_menus() {
	//Hide the "Tools → Safe Redirect Manager" menu.
	remove_submenu_page('tools.php', 'edit.php?post_type=redirect_rule');
}

add_action('admin_menu', 'plt_hide_safe_redirect_manager_menus', 15);

Where do I put this code?