Update pytest-cov requirement in the all-dependencies group

Updates the requirements on [pytest-cov](https://github.com/pytest-dev/pytest-cov) to permit the latest version.

Updates `pytest-cov` to 6.0.0
- [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:production
  dependency-group: all-dependencies
...

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

requirements-test.txt

@@ -5,7 +5,7 @@ coverage~=7.6
 flake8~=7.1
 mock~=5.1
 pytest~=8.3
-pytest-cov~=5.0
+pytest-cov~=6.0
 pytest-gitignore~=1.3
 pytest-mock~=3.14
 setuptools>=65.5.1 # not directly required, pinned by Snyk to avoid a vulnerability