Following-on from Ia3a0358249e9ed3d766b1b61535f2f6d67d4eb2d, this
removes the publishing from the static site, which is now happening to
AFS.
The site_tarballs secret is no longer required. The two jobs still
using it have a parent of publish-openstack-artifacts so should not
need a separate secret.
Depends-On: https://review.opendev.org/706732
Change-Id: I1b1db7d2451d7fb1fdd7921e7c9efd0e020fbce6