devel/plan9port: unbreak, update, and undeprecate the port (+)

- Fix the conflict with badly named kcmp(2) syscall introduced in
  recent FreeBSD-CURRENT/14.1
- Update to the latest GitHub commit, shorten the GH_TAGNAME, and
  merge two installation targets into one (which still begs for a
  further pre/post-stage separation and cleanup)

Fixes:	d846b489
PR:	278145