Replace the java.util.Objects.newIdentity() method with the version slated for JDK 17
and remove the previous placeholder.

/**
 * {@return a new instance of an unspecified class}
 * The object has a unique identity; no other references to it exist.
 * It can be used for synchronization, or where a placeholder Object is needed.
 * Use this method to avoid relying on the {@linkplain Object#Object() Object constructor}.
 *
 * @since 17
 */
public static Object newIdentity() {...}