How to Hide the "WP-DB Backup" Admin Menu

function plt_hide_wp_database_backup_menus() {
	//Hide the "Tools → WP-DB Backup" menu.
	remove_submenu_page('tools.php', 'wp-database-backup');
}

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

Where do I put this code?