filesystems:py-libzfs: fix the build on FreeBSD 16

freebsd-src recently removed ZFS's libuutil[^1]. Patch py-libzfs so it
won't attempt to link to that library on FreeBSD 16.

[^1]: https://cgit.freebsd.org/src/commit/?id=66e85755595

Sponsored by: ConnectWise
PR: 291530
Approved by: brd (ports)