Corrected section indentation in unit tests contributor docs.
@@ -476,12 +476,12 @@ You can also use the ``DJANGO_TEST_PROCESSES`` environment variable for this
purpose.
Tips for writing tests
-----------------------
+======================
.. highlight:: python
Isolating model registration
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+----------------------------
To avoid polluting the global :attr:`~django.apps.apps` registry and prevent
unnecessary table creation, models defined in a test method should be bound to
