Remove legacy-devstack-unit-tests job
The job is in-tree, remove it.
Depends-On:
- build-openstack-sphinx-docs:
branches: ^master
- openstack-tox-bashate
- - legacy-devstack-unit-tests
- ironic-tempest-dsvm-ipa-wholedisk-bios-agent_ipmitool-tinyipa:
voting: false
- legacy-devstack-dsvm-updown:
