Remove barbican-tempest-plugin from blacklist

This commit removes barbican-tempest-plugin from the blacklist. The
patch[1] got already merged. The plugin should work for the sanity now.

[1] https://review.opendev.org/#/c/634631/

Change-Id: I34d119c58afa6b3c728d1a540b4ea1df27d9c4d0
1 file changed