.pre-commit-config.yaml:
- flake8 has been removed as it's a wrapper for pyflakes, which parses
the py files itself, meaning it's faster than pylint, but less powerful.
It seems it was not active as we had only two #noqa but no warnings.
- autopep8-wrapper has been removed so the committer is in control.

pre-commit.hook:
- git_pep8_commit_hook has been removed as pylint already checks for
PEP8 conformance.
- pylint is now run after the lightweight pre-commit.com hooks.