chore(deps-dev): update flake8 requirement

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@4.0.0...6.1.0)

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

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

pyproject.toml

@@ -42,7 +42,7 @@ test = [
     "pytest-mock >=3.0.0,<4.0.0",
     "black ==23.7.0",
     "mypy >=1.0.0",
-    "flake8 >=4.0.0,<5.0.0",
+    "flake8 >=4.0.0,<7.0.0",
     "isort >=5.0.0,<7.0.0",
     "ruff ==0.0.285",
     "types-requests >=2.20.0,<3.0.0",