Update pytest-cov requirement from ~=5.0 to ~=6.0 in /.dev

Updates the requirements on [pytest-cov](https://github.com/pytest-dev/pytest-cov) to permit the latest version.
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v5.0.0...v6.0.0)

---
updated-dependencies:
- dependency-name: pytest-cov
  dependency-type: direct:development
...

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

.dev/requirements_dev.txt

@@ -6,7 +6,7 @@ invoke~=2.2
 pre-commit~=4.0
 pylint~=3.3
 pytest~=8.3
-pytest-cov~=5.0
+pytest-cov~=6.0
 
 # httpx is necessary due to the use of fastapi/starlette's TestClient
 # See https://fastapi.tiangolo.com/tutorial/testing/?h=testclient#using-testclient