build(deps): update pytest-cov requirement from <5,>=4 to >=4,<6

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@v4.0.0...v5.0.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

requirements/testing.txt

@@ -1,3 +1,3 @@
-pytest-cov>=4,<5
+pytest-cov>=4,<6
 packaging>=20,<24
 validators>=0.19,<0.23