Update flake8 requirement from ^4.0.1 to ^5.0.4 (#74)

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Release notes](https://github.com/pycqa/flake8/releases)
- [Commits](PyCQA/flake8@4.0.1...5.0.4)

---
updated-dependencies:
- dependency-name: flake8
  dependency-type: direct:development
...

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Author: dependabot[bot]

pyproject.toml

@@ -23,7 +23,7 @@ pydantic = "^1.9.0"
 black = "^22.1"
 isort = "^5.9.3"
 mypy = "^0.961"
-flake8 = "^4.0.1"
+flake8 = "^5.0.4"
 pytest = "^7.0.0"
 pytest-asyncio = "^0.18.0"
 pytest-mock = "^3.6.1"