python:gp_cert_auto_enrol: fix GUID stringification

python:gp_cert_auto_enrol: fix GUID stringification

We were using some broken ad-hoc unpacking to do what the ndr
unpacker does perfectly well.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15839

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Jennifer Sutton <jennifersutton@catalyst.net.nz>
Autobuild-User(master): Douglas Bagnall <dbagnall@samba.org>
Autobuild-Date(master): Tue Mar 25 05:21:49 UTC 2025 on atb-devel-224

(cherry picked from commit 47ff42232048c008a7b361a948e5ac79311b5458)

Autobuild-User(v4-22-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-22-test): Thu Apr 17 12:49:13 UTC 2025 on atb-devel-224