dns/samba-nsupdate: Deprecate
Based on the following comment by michaelo@:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=247802#c8
Set a deprecation date far in the future, so that users of this port
have the time to either let us know it is still useful.
PR: 291687
Differential Revision: https://reviews.freebsd.org/D54182