Update flake8 requirement from ==6.0.* to ==7.0.* in /requirements

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@6.0.0...7.0.0)

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

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

requirements/requirements-dev.txt

@@ -5,7 +5,7 @@ pytest-recording==0.12.*
 pytest-cov==4.1.*
 pytest-env==1.0.*
 pytest-html==3.2.*
-flake8==6.0.*
+flake8==7.0.*
 pydocstyle>=6.1
 black>=22.6
 isort>=5.12