Revert "Merge branch '41-python-slim' into 'master'"
This reverts merge request !49 (merged) which breaks some builds. E.g. https://gitlab.developers.cam.ac.uk/uis/devops/infra/dockerimages/-/jobs/150620
This reverts merge request !49 (merged) which breaks some builds. E.g. https://gitlab.developers.cam.ac.uk/uis/devops/infra/dockerimages/-/jobs/150620