build(deps): bump pytest-cov in /testing/plugins_integration

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:production
  update-type: version-update:semver-major
...

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

testing/plugins_integration/requirements.txt

@@ -2,7 +2,7 @@ anyio[curio,trio]==3.3.2
 django==3.2.7
 pytest-asyncio==0.15.1
 pytest-bdd==4.1.0
-pytest-cov==2.12.1
+pytest-cov==3.0.0
 pytest-django==4.4.0
 pytest-flakes==4.0.3
 pytest-html==3.1.1