Cleanup: do not include ch.qos.logback.slf4j in the target file

This way we don't enable debug logging for bundles using slf4j. If we
choose to do that, we'll need to setup a special target platform which
includes logback and then make sure that the correct configuration is
picked up.

git-svn-id: https://svn.apache.org/repos/asf/sling/branches/tooling-ide-vlt@1525022 13f79535-47bb-0310-9956-ffa450edef68