Bump pytest-cov from 2.8.1 to 5.0.0 in /requirements

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 2.8.1 to 5.0.0.
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v2.8.1...v5.0.0)

---
updated-dependencies:
- dependency-name: pytest-cov
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

requirements/tests.txt

@@ -1,5 +1,5 @@
 pytest==5.2.4
-pytest-cov==2.8.1
+pytest-cov==5.0.0
 cov-core==1.15.0
 
 ovos-stt-plugin-selene>=0.0.3a3