Update pytest-cov requirement from ==2.11.* to ==3.0.*

Updates the requirements on [pytest-cov](https://github.com/pytest-dev/pytest-cov) to permit the latest version.
- [Release notes](https://github.com/pytest-dev/pytest-cov/releases)
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v2.11.0...v3.0.0)

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

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

Author: dependabot[bot]

requirements-test.txt

@@ -1,5 +1,5 @@
 pytest==6.2.*
-pytest-cov==2.11.*
+pytest-cov==3.0.*
 black==20.8b1
 isort==5.7.*
 flake8==4.0.*