⬆️ Update flake8 requirement from ~=6.1.0 to ~=7.0.0

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@6.1.0...7.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements-dev.txt

@@ -4,5 +4,5 @@ assertpy~=1.1.0
 pytest==7.4.3
 pytest-cov==4.1.0
 setuptools==68.2.2
-flake8~=6.1.0
+flake8~=7.0.0
 mutmut~=2.4.4