Update pre-commit for flake8 move

[adamchainz]

See: https://twitter.com/codewithanthony/status/1378746934928699396

[adamchainz]

Test failures look maybe related to Django 3.2 release

_____ TestNaiveDayLightSavingTimeTimeZoneDateTimeField.test_invalid_inputs _____

tests/test_fields.py:621: in test_invalid_inputs

    assert exc_info.value.detail == expected_failure, \

E   AssertionError: input value: '2017-03-12T02:30:00'

E   assert [ErrorDetail(...de='invalid')] == ['Invalid dat...a/New_York".']

E     At index 0 diff: ErrorDetail(string='Datetime has wrong format. Use one of these formats instead: YYYY-MM-DDThh:mm[:ss[.uuuuuu]][+HH:MM|-HH:MM|Z].', code='invalid') != 'Invalid datetime for the timezone "America/New_York".'

E     Use -v to get the full diff