Update flake8 requirement from <7.0.0,>=6.0.0 to >=6.0.0,<8.0.0

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@6.0.0...7.1.1)

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

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

pyproject.toml

@@ -40,7 +40,7 @@ build-backend = "setuptools.build_meta"
 dev = [
     "autopep8 >=2.0.2, <3.0",
     "Flake8-pyproject>=1.2.3, <2.0.0",  # To read flake8 configuration from pyproject.toml
-    "flake8 >=6.0.0, <7.0.0",
+    "flake8 >=6.0.0, <8.0.0",
     "flake8-print >=5.0.0, <6.0.0",
     "flake8-quotes >=3.3.2",
     "pytest",  # Let OpenFisca-Core decide pytest version