Remove unnecessary flake8 exclude (#416)
Remove unnecessary flake8 exclude (#416)

Modern flake8 has a good default for exclude that includes the tox
directory.

https://gitlab.com/pycqa/flake8/blob/2b333fad1abe0bdb2e04132eabb0822e6ce63888/src/flake8/defaults.py#L4-14
html5lib/html5lib-python,html5lib/html5lib-python,html5lib/html5lib-python