How to Hide the "Inactive users" Admin Menu

function plt_hide_inactive_user_deleter_menus() {
	//Hide the "Users → Inactive users" menu.
	remove_submenu_page('users.php', 'inactive-user-deleter/inactive-user-deleter.php');
}

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

Where do I put this code?