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](pytest-dev/pytest-cov@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] <[email protected]>

Author: dependabot[bot]

poetry.lock

@@ -31,7 +31,7 @@ blacksheep = ">=1.0.7"
 [tool.poetry.dev-dependencies]
 pytest = "^6.2.4"
 pytest-xdist = "^2.3.0"
-pytest-cov = "^2.12.1"
+pytest-cov = "^3.0.0"
 tox = "^3.24.0"
 isort = "^5.10.1"
 flake8 = "^3.9.2"