test: fix dependency groups

Previously, the test dependencies were not installed,
which resulted in a call to an incorrect `pytest` executable.

Author: Agrendalath

tox.ini

@@ -8,17 +8,18 @@ ignore = D001
 
 [testenv]
 runner = uv-venv-lock-runner
-dependency_groups = django42
-uv_resolution = highest
-allowlist_externals =
-    python
+dependency_groups =
+    test
+    django42
 commands =
     python manage.py check
     python manage.py makemigrations learning_credentials --check --dry-run --verbosity 3
     pytest {posargs}
 
 [testenv:py{311,312}-django52]
-dependency_groups = django52
+dependency_groups =
+    test
+    django52
 
 [testenv:docs]
 dependency_groups =