build(deps): Bump django in /testing/plugins_integration (#13210)

Bumps [django](https://github.com/django/django) from 5.1.5 to 5.1.6.
- [Commits](django/django@5.1.5...5.1.6)

---
updated-dependencies:
- dependency-name: django
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

testing/plugins_integration/requirements.txt

@@ -1,5 +1,5 @@
 anyio[trio]==4.8.0
-django==5.1.5
+django==5.1.6
 pytest-asyncio==0.25.3
 pytest-bdd==8.1.0
 pytest-cov==6.0.0