This server has been replaced by ze01.opendev.org running Focal. Lets
remove the old ze01.openstack.org from inventory so that we can delete
the server. We will follow this up with a rotation of new focal servers
being put in place.
This also renames the xenial executor in testing to ze12.openstack.org
as that will be the last one to be rotated out in production. We will
remove it from testing at that point as well.
We also remove a completely unused zuul-executor-opendev.yaml group_vars
file to avoid confusion.
Change-Id: Ida9c9a5a11578d32a6de2434a41b5d3c54fb7e0c