Fixed docs build with sphinxcontrib-spelling 7.5.0+.

sphinxcontrib-spelling 7.5.0+ includes captions of figures in the set
of nodes for which the text is checked.

docs/topics/db/models.txt

@@ -1474,7 +1474,7 @@ For example, if you had ``organic.py`` and ``synthetic.py`` in the ``models``
 directory:
 
 .. code-block:: python
-    :caption: myapp/models/__init__.py
+    :caption: ``myapp/models/__init__.py``
 
     from .organic import Person
     from .synthetic import Robot