Bump pytest-cov from 5.0.0 to 6.0.0 in /requirements

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 5.0.0 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
  update-type: version-update:semver-major
...

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

requirements/requirements-testing.txt

@@ -2,7 +2,7 @@
 
 # testing
 pytest==8.3.3
-pytest-cov==5.0.0
+pytest-cov==6.0.0
 
 # linting & formatting
 black==24.10.0