Temporarily disable flake8 pre-commit hook.

[NikoOinonen]

I'm suggesting that we temporarily disable the flake8 pre-commit hook, since there has been no consensus on whether black should be enabled or not (#96). At the moment the pre-commit never succeeds because of all the code style problems, so it's mostly just an annoyance since in practice you have to use the --no-verify option every time or manually disable the check locally.

[mondracek]

Let's do it. But we should reactivate it later when we are ready to review all the white-space formatting issues. Comparing and merging too branches that do not differ much but differ a lot in the white spaces is a hell.