Update pytest-cov requirement from <5.1,>=4.1.0 to >=4.1.0,<6.1

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@v4.1.0...v6.0.0)

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

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

requirements/test.txt

@@ -2,4 +2,4 @@
 
 django-linear-migrations>=2.8.0,<2.14
 pytest-django>=4.5.2,<4.10
-pytest-cov>=4.1.0,<5.1
+pytest-cov>=4.1.0,<6.1