remove publish-openstack-sphinx-docs-python3 job
remove publish-openstack-sphinx-docs-python3 job

We no longer need this job since we are going to use
publish-openstack-tox-docs instead.

Depends-On: https://review.openstack.org/580488
Change-Id: I3d16c4ebaed177e1cbb2930e45007842d9962e4a
Signed-off-by: Doug Hellmann <0798ebecfb7bc4dfb9d0445c2fa030eb64e1fa1c@doughellmann.com>

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