[5.0.x] Applied Black's 2024 stable style.

https://github.com/psf/black/releases/tag/24.1.0

Backport of 305757aec1 from main

tests/save_delete_hooks/models.py

@@ -4,6 +4,7 @@ Adding hooks before/after saving and deleting
 To execute arbitrary code around ``save()`` and ``delete()``, just subclass
 the methods.
 """
+
 from django.db import models