[1.10.x] Fixed typo in docs/topics/auth/customizing.txt.

Backport of da4c0e8cc9 from master

docs/topics/auth/customizing.txt

@@ -393,7 +393,7 @@ user model, even if the default :class:`~django.contrib.auth.models.User` model
 is sufficient for you. This model behaves identically to the default user
 model, but you'll be able to customize it in the future if the need arises::
 
-    from django.conf.auth.models import AbstractUser
+    from django.contrib.auth.models import AbstractUser
 
     class User(AbstractUser):
         pass