Bump tempest version in requirements.txt

Tempest fixed server SSHABLE bug and the new way/fix is
consumed by cinder-tempest-plugin
- https://review.opendev.org/c/openstack/cinder-tempest-plugin/+/881764

To keep requirements.txt lower bound up to dated, this bumping
the Tempest version to 34.2.0 which include the SSHABLE fix
- https://review.opendev.org/c/openstack/releases/+/882356

Change-Id: I10137b03cc2e19f4f64220ad0c4cc8ee7c952122
1 file changed