Although Tacker docs move to new docs PTI jobs (https://review.openstack.org/#/c/552046/), the sphinx is still using legacy pbr runner. This patch works futher jobs: - Remove legacy pbr runner, [pbr] section. - Remove [build_sphinx] section. as described in: http://lists.openstack.org/pipermail/openstack-dev/2018-March/128594.html Change-Id: Ic65ed5ec145fa8a356fe28f86c3a69e3d20ef3c2