Re-upgrade logback dep to runtime.
Re-upgrade logback dep to runtime.

Require logback for at run time, not just test time; it would be good to downgrade it again, but that will have to wait.

vaibhav345/lenskit,martinlaz/lenskit,tajinder-txstate/lenskit,amaliujia/lenskit,aglne/lenskit,tajinder-txstate/lenskit,blankazucenalg/lenskit,tajinder-txstate/lenskit,linjunleo/lenskit,vijayvani/Lenskit,kluver/lenskit,amaliujia/lenskit,vaibhav345/lenskit,vaibhav345/lenskit,blankazucenalg/lenskit,chrysalag/lenskit,linjunleo/lenskit,binweiwu/lenskit,martinlaz/lenskit,aglne/lenskit,binweiwu/lenskit,chrysalag/lenskit,vaibhav345/lenskit,tajinder-txstate/lenskit,kluver/lenskit,kluver/lenskit,kluver/lenskit,vijayvani/Lenskit,kluver/lenskit