fix: pass pytest lms UpdateThreadTest

[Carlos-Muniz]

As part of #36, several tests have been discovered that are not passing in tutor, but passing in devstack. The following tests may not be run by tutor, or may be failing in tutor.

lms/djangoapps/discussion/rest_api/tests/test_api.py::UpdateThreadTest::

• test_thread_un_abuse_flag_for_moderator_role_2__True__False_

For more information about the tests that passed, failed, skipped, or never ran, see the spreadsheet with all the tests.

[Carlos-Muniz]

This test does pass in tutor. See #155 for more details.