Bump from Python 3.11 to 3.12 as default FreeBSD version

For NetBox service, we can actually use "python3" to use the virtual
environment version. That will launch NetBox like this:
/srv/netbox/venv/bin/python3 /srv/netbox/venv/bin/gunicorn --pid ...

Differential Revision: https://devcentral.nasqueron.org/D4116