INCR-255 Run python-modernize on lms/djangoapps/notes (#20565)

* run python modernize

* run isort

* Fix quality

lms/djangoapps/notes/api.py

@@ -1,8 +1,10 @@
 from __future__ import absolute_import
+
 import collections
 import json
 import logging
 
+import six
 from django.contrib.auth.decorators import login_required
 from django.core.exceptions import ValidationError
 from django.http import Http404, HttpResponse
@@ -11,7 +13,6 @@ from opaque_keys.edx.keys import CourseKey
 from courseware.courses import get_course_with_access
 from notes.models import Note
 from notes.utils import notes_enabled_for_course
-import six
 
 log = logging.getLogger(__name__)