Fix typo in publish-infra-index
Fix typo in publish-infra-index

It's "subpath" not "sub_path" - fix typo in publish-infra-index so that
publishing works again.

The typo was introduced in https://review.opendev.org/662604, this
change should really fix the job.

Change-Id: Ib0d40aff3b902c6662733fcfdf90b54c12c52558

openstack-infra/project-config,openstack-infra/project-config