Refs #23919 -- Removed most of remaining six usage

Thanks Tim Graham for the review.

tests/model_forms/models.py

@@ -16,7 +16,6 @@ from django.core.exceptions import ValidationError
 from django.core.files.storage import FileSystemStorage
 from django.db import models
 from django.utils._os import upath
-from django.utils.six.moves import range
 
 temp_storage_dir = tempfile.mkdtemp()
 temp_storage = FileSystemStorage(temp_storage_dir)