build(deps-dev): update flake8 requirement from <7,>=6.0.0 to >=6.0.0,<8

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] <[email protected]>

dev-requirements.txt

@@ -2,7 +2,7 @@ black>=23,<24
 flake8-annotations>=2.7.0,<4
 flake8-isort>=6.0.0,<7
 flake8-print>=5.0.0,<6
-flake8>=6.0.0,<7
+flake8>=6.0.0,<8
 isort>=5.10.1,<6
 pre-commit>=2.10.1,<4
 pytest>=7.4.3,<7.5