Update flake8 requirement from ==4.0.* to ==7.1.*

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@4.0.0...7.1.0)

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

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

requirements-test.txt

@@ -1,5 +1,5 @@
 black==22.3.0
-flake8==4.0.*
+flake8==7.1.*
 isort==5.10.*
 mock==4.0.3
 mongomock==4.1.*