Bump flake8 from 3.9.2 to 4.0.1

Bumps [flake8](https://github.com/pycqa/flake8) from 3.9.2 to 4.0.1.
- [Release notes](https://github.com/pycqa/flake8/releases)
- [Commits](https://github.com/pycqa/flake8/compare/3.9.2...4.0.1)

---
updated-dependencies:
- dependency-name: flake8
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements-dev.txt

@@ -18,7 +18,7 @@ filelock==3.0.12
     # via
     #   tox
     #   virtualenv
-flake8==3.9.2
+flake8==4.0.1
     # via -r requirements-dev.in
 iniconfig==1.1.1
     # via pytest
@@ -38,9 +38,9 @@ py==1.10.0
     # via
     #   pytest
     #   tox
-pycodestyle==2.7.0
+pycodestyle==2.8.0
     # via flake8
-pyflakes==2.3.1
+pyflakes==2.4.0
     # via flake8
 pyparsing==2.4.7
     # via packaging