Update pytest-cov requirement from ~=2.11 to ~=3.0 (#1424)

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] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Daniël van Noord <[email protected]>

Author: dependabot[bot]

requirements_test.txt

@@ -3,7 +3,7 @@
 coveralls~=3.3
 coverage~=5.5
 pre-commit~=2.17
-pytest-cov~=2.11
+pytest-cov~=3.0
 tbump~=6.3.2
 types-typed-ast; implementation_name=="cpython" and python_version<"3.8"
 types-pkg_resources==0.1.3