chore(deps-dev): 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](PyCQA/flake8@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] <[email protected]>

Author: dependabot[bot]

Diff for: poetry.lock

@@ -32,7 +32,7 @@ email-validator = {version = "*", optional = true }
 coverage = {extras = ["toml"], version = "^6.1"}
 pytest = "^6.2.5"
 black = "^21.10.b0"
-flake8 = "^3.9.0"
+flake8 = "^4.0.1"
 flake8-black = "^0.2.3"
 flake8-builtins = "^1.5.3"
 flake8-comprehensions = "^3.7.0"