Update flake8 requirement from <2.5,>=2.4.1 to >=2.4.1,<3.8
Update flake8 requirement from <2.5,>=2.4.1 to >=2.4.1,<3.8

Updates the requirements on [flake8](https://gitlab.com/pycqa/flake8) to permit the latest version.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/2.4.1...3.7.7)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
edelbluth/blackred,edelbluth/blackred