[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/one_to_one/models.py

@@ -5,6 +5,7 @@ To define a one-to-one relationship, use ``OneToOneField()``.
 
 In this example, a ``Place`` optionally can be a ``Restaurant``.
 """
+
 from django.db import models