build(deps): Bump pytest-mock in /testing/plugins_integration

Bumps [pytest-mock](https://github.com/pytest-dev/pytest-mock) from 3.8.2 to 3.9.0.
- [Release notes](https://github.com/pytest-dev/pytest-mock/releases)
- [Changelog](https://github.com/pytest-dev/pytest-mock/blob/main/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest-mock/compare/v3.8.2...v3.9.0)

---
updated-dependencies:
- dependency-name: pytest-mock
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

testing/plugins_integration/requirements.txt

@@ -6,7 +6,7 @@ pytest-cov==4.0.0
 pytest-django==4.5.2
 pytest-flakes==4.0.5
 pytest-html==3.1.1
-pytest-mock==3.8.2
+pytest-mock==3.9.0
 pytest-rerunfailures==10.2
 pytest-sugar==0.9.5
 pytest-trio==0.7.0