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

Bumps [pytest-django](https://github.com/pytest-dev/pytest-django) from 3.10.0 to 4.0.0.
- [Release notes](https://github.com/pytest-dev/pytest-django/releases)
- [Changelog](https://github.com/pytest-dev/pytest-django/blob/master/docs/changelog.rst)
- [Commits](https://github.com/pytest-dev/pytest-django/compare/v3.10.0...v4.0.0)

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

testing/plugins_integration/requirements.txt

@@ -3,7 +3,7 @@ django==3.1.2
 pytest-asyncio==0.14.0
 pytest-bdd==4.0.1
 pytest-cov==2.10.1
-pytest-django==3.10.0
+pytest-django==4.0.0
 pytest-flakes==4.0.2
 pytest-html==2.1.1
 pytest-mock==3.3.1