[train]: add designate-tempest-plugin as req

Add designate-tempest-plugin to required-projects of
neutron-tempest-plugin-designate-scenario-train and pin it to 0.7.0.
This should avoid the client initialization issue bring in by [1].

[1]: https://review.opendev.org/c/openstack/neutron-tempest-plugin/+/800291

Change-Id: Ib58f0cf251b84c21db0f4b8defd213c770739134
Closes-Bug: #1950346
1 file changed