testing/plugins_integration: update Django (#13463)

Fix some dependabot security notices. For some reason dependabot doesn't
manage to create a PR for it on its own.

Author: bluetech

testing/plugins_integration/requirements.txt

@@ -1,5 +1,5 @@
 anyio[trio]==4.9.0
-django==5.1.7
+django==5.2.1
 pytest-asyncio==0.26.0
 pytest-bdd==8.1.0
 pytest-cov==6.1.1