Avoid skipping tests when build Python wheels

[jesper-friis]

Currently, when building Python wheels, some tests are skipped. See e.g. https://github.com/SINTEF/dlite/actions/runs/5901236903/job/16007030512?pr=594#step:6:882

Figure out why this is happening and ensure that the tests run.

I am little surprised that the tests are not running, since we install all dependencies should be installed in the templates for the docker images in .github/docker/Dockerfile-*.template. Maybe an old version of the docker image is picked up?