sysutils/openzfs*: Minor port housekeeping

Update the WWW to the official openzfs/zfs github repo, since the ZoF
repo is no longer used after merging to ZoL and renaming to openzfs/zfs.

While here, make a few small changes suggested by portlint.

Approved by: lwhsu (implicit)
PR: 267453
Sponsored by: iXsystems, Inc.