get rid of weird before_quiz_submission_types attr

Test plan: specs pass

Change-Id: Ibfcaf313345277daa2a1f2f50741b7e3131fc9ec
Reviewed-on: https://gerrit.instructure.com/37365
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>
QA-Review: Cameron Matheson <cameron@instructure.com>