Bump isort version to 5.12.0
Fixes crash in pre-commit hook, see e.g. https://levelup.gitconnected.com/fix-runtimeerror-poetry-isort-5db7c67b60ff
Fixes crash in pre-commit hook, see e.g. https://levelup.gitconnected.com/fix-runtimeerror-poetry-isort-5db7c67b60ff