CI: Use Django 5.2 or 6.0 depending on Python version

Affects `tests` dependency group only.

Author: intgr

pyproject.toml

@@ -49,7 +49,8 @@ tests = [
   "pytest-shard==0.1.2",
   "pytest-xdist==3.8.0",
   # Django deps:
-  "django==5.2.9",
+  "django==5.2.9; python_version < '3.12'",
+  "django==6.0; python_version >= '3.12'",
   "mysqlclient==2.2.7",
   "psycopg2-binary==2.9.11",
   "jinja2==3.1.6",