[5.2.x] Fixed #36159 -- Removed the empty import example in the custom shell docs.

This can be achieved with the --no-imports flag.

Backport of b84478ae953d049a1da42c3d0ef3ab3a9467b649 from main.

docs/howto/custom-shell.txt

@@ -42,16 +42,3 @@ The above customization adds :func:`~django.urls.resolve` and
 :func:`~django.urls.reverse` to the default namespace, which includes all
 models from all apps. These two functions will then be available when the
 shell opens, without a manual import statement.
-
-If you prefer to not have models automatically imported, create a custom
-``get_namespace()`` that excludes the ``super().get_namespace()`` call:
-
-.. code-block:: python
-    :caption: ``polls/management/commands/shell.py``
-
-    from django.core.management.commands import shell
-
-
-    class Command(shell.Command):
-        def get_namespace(self):
-            return {}