[deps] Update pytest-cov requirement from ~=6.1.1 to ~=6.2.1

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@v6.1.1...v6.2.1)

---
updated-dependencies:
- dependency-name: pytest-cov
  dependency-version: 6.2.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements-test.txt

@@ -1,4 +1,4 @@
-pytest-cov~=6.1.1
+pytest-cov~=6.2.1
 openwisp-utils[qa,selenium,channels-test] @ https://github.com/openwisp/openwisp-utils/tarball/1.2
 django_redis~=5.4.0
 mock-ssh-server~=0.9.1