Update flake8 requirement from ~=6.1 to ~=7.0

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:production
...

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

requirements-test.txt

@@ -2,7 +2,7 @@
 async-timeout
 asynctest~=0.13
 colorlog~=6.7
-flake8~=6.1
+flake8~=7.0
 flake8-docstrings~=1.7
 mypy==1.7.0
 pylint~=3.0