For junit-5 it's sufficient and recommended to just import the packages
needed for compilation. Alternatively it's also possible to require the
junit-jupiter-api bundle.

Both is already proposed by default and in both cases it's not necessary
to require the junit-4 bundle (org.junit) too.

Furthermore the current code seems to be partially incorrect, because
actually package names have to be checked while it seems that the code
assumed bundle names (which only coincidentally match).

As this extra proposal also complicates the code significantly, it is
removed with the recommendation to use the other standard proposals in
case of missing JUnit-5 dependencies too.

Removing it also avoids the need to handle the JUnit-6 case too.