Bump pytest-cov from 2.12.1 to 3.0.0

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 2.12.1 to 3.0.0.
- [Release notes](https://github.com/pytest-dev/pytest-cov/releases)
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest-cov/compare/v2.12.1...v3.0.0)

---
updated-dependencies:
- dependency-name: pytest-cov
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

requirements-dev.txt

@@ -10,7 +10,7 @@ flake8-tidy-imports==4.4.1
 mypy==0.910
 pytest==6.2.5
 pytest-asyncio==0.15.1
-pytest-cov==2.12.1
+pytest-cov==3.0.0
 pytest-mock==3.6.1
 pytest-random-order==1.0.4
 isort==5.9.3