Docker workflow failure

[eddiebergman]

Fails due to required pytest-cases dependancy requirement in testing, e.g. https://github.com/automl/auto-sklearn/runs/6936821659?check_suite_focus=true

Ideally we don't need to update this seperatly

[eddiebergman]

Turns out that scikit learn stopped supporting Python 3.7 from v1.1 onwards.