Remove 'default_app_config'

This is no longer necessary since we don't support Django < 3.2, which
is where the automatic configuration behavior was added [1].

[1] https://docs.djangoproject.com/en/4.0/releases/3.2/#automatic-appconfig-discovery

Signed-off-by: Stephen Finucane <[email protected]>

Author: stephenfin

patchwork/__init__.py

@@ -8,5 +8,3 @@
 VERSION = (3, 1, 0, 'alpha', 0)
 
 __version__ = get_latest_version(VERSION)
-
-default_app_config = 'patchwork.apps.PatchworkAppConfig'