Revert "Update requires for new build of slf4j."

This reverts commit e384d6a540a2fe405b60159cd0ec252238d32389.

Buildroot was reverted to previous slf4j so this won't be necessary
anymore, and it's causing problems for all hotfix builds.
Revert "Change dep to slf4j-api."

This reverts commit 59a581c0106adfffe6906c97287be230f708d8a2.

Back to old slf4j as this was causing problems.
Automatic commit of package [candlepin] release [0.8.28.5-1].