Subscription resources of a job resource will be destroyed in Gram4 after the
last notification had been sent. There’s no need for the client to do that
manually anymore.

Reason for that is that the client don't have to care for destruction of
subscription resources anymore and the server's persistence directory does
not get heaped up with forgotten subscription resources.

A client can do so however, but this must be done before the job resource is
destroyed due to architectural decisions in Java WS Core.