chore: Update flake8 requirement from ~=5.0 to ~=6.1

Updates the requirements on [flake8](https://github.com/pycqa/flake8) to permit the latest version.
- [Commits](PyCQA/flake8@5.0.0...6.1.0)

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

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

dev-requirements.txt

@@ -1,7 +1,7 @@
 autoflake~=1.7
 black~=23.3
 dbt-tests-adapter~=1.5.4
-flake8~=5.0
+flake8~=6.1
 Flake8-pyproject~=1.2
 isort~=5.11
 moto~=4.1.14