After a bug fix in Tycho it's not necessary anymore to specify the
complete set of junit bundles explicitly, in order to ensure that
JUnit-6 bundles are not present:
- https://github.com/eclipse-tycho/tycho/pull/5526

This reverts most of the workarounds from
- https://github.com/eclipse-pde/eclipse.pde/pull/2004
- https://github.com/eclipse-pde/eclipse.pde/pull/2054