remove CI workflow for Hound style checker

[branfosj]

We do flake8 linting in https://github.com/easybuilders/easybuild-framework/blob/develop/.github/workflows/linting.yml so we no longer need the hound.

Picked up from @Flamefire's comment at #5174 (comment)

From http://help.houndci.com/en/articles/2138537-flake8 it looks like we have flake8 3.6.0 and that was released in 2018.

[Flamefire]

Just noticed: The hound posts just comments but doesn't fail CI. So we could keep it and simply close/resolve/ignore the wrong ones. There doesn't seem to be too many.
Would be great if we had a commenter with a recent-ish flake8 though.

[Flamefire]

This seems to be getting urgent: CI now fails with

Hound — We've encountered an error while reviewing your code.

But no further mention on what the issue is. See e.g. #5185
That seems to be some internal error, so nothing we can do anything about

[Crivella]

LGTM

also this is an easy revert that does not break anything in case the bot gets fixed and we decide we still need it.

Also i think this should be enough to stop the flake check running, but we should also disconnect the bot from the account/repo itself to fully remove it

[Crivella]

Going in, thanks @branfosj!