update libraries (major bump) gives some false positives

[PietroPasotti]

see:
canonical/traefik-k8s-operator#326

In this case, traefik maintains both a v1 and a v2 library. Not just because traefik owns the libs and still has to maintain both, but also because the charm still needs to be compatible with both!

The logic should be refined:
from: for each lib version, open an issue if there is a more recent version.
to: for each lib, only open an issue if the most recent version present in this repo has a more recent version.