Update flake8 requirement from <=6.1 to <=7.0.0

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@0.1...7.0.0)

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

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

Author: dependabot[bot]

requirements-dev.txt

@@ -1,5 +1,5 @@
 black<=24.3.0
-flake8<=6.1
+flake8<=7.0.0
 mypy<=1.9.0
 pytest<=8.1.1
 pytest-asyncio<0.24.0