allow quiz stats feature flag to be used

fixes CNVS-13612

test plan:
  - go to the feature flags page
  - quiz stats should no longer have a 'hidden' badge

Change-Id: I55bb4fa493701e2bce99ec2a8b8d586a76088ea2
Reviewed-on: https://gerrit.instructure.com/36390
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jason Madsen <jmadsen@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>