[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/serializers/models/base.py

@@ -4,6 +4,7 @@ Serialization
 ``django.core.serializers`` provides interfaces to converting Django
 ``QuerySet`` objects to and from "flat" data (i.e. strings).
 """
+
 from decimal import Decimal
 
 from django.db import models