Remove obsolete docs job from neutron-tempest-plugin-jobs

Currently, neutron repo builds docs twice: with the PTI job
openstack-tox-docs which is part of publish-openstack-docs-pti and with
the obsolete job build-openstack-sphinx-docs which is part of
neutron-tempest-plugin-jobs.

The template neutron-tempest-plugin-jobs is only used for this repo and
for neutron.

Fix:
* Remove the obsolete doc building job so that only the new PTI job is used.

* Add the template build-openstack-docs-pti so that the new PTI jobs run
  on this repo.

Change-Id: I7e5cb3a3fc1b6da0f4b335b631fbaa071cf74631
1 file changed