Refs #23919 -- Removed most of remaining six usage

Thanks Tim Graham for the review.

tests/delete/tests.py

@@ -3,7 +3,6 @@ from math import ceil
 from django.db import IntegrityError, connection, models
 from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE
 from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
-from django.utils.six.moves import range
 
 from .models import (
     MR, A, Avatar, Base, Child, HiddenUser, HiddenUserProfile, M, M2MFrom,