remove 'show student quiz results' from quiz menu unless moderate feature enabled

fixes CNVS-13591

test plan:
  - enable draft state and quiz stats features
  - create and visit a quiz
  - the dropdown menu should not include the option to 'show student quiz results'

  - enable quiz moderate feature
  - the dropdown menu should include the option to 'show student quiz results'

Change-Id: Iddeb1d09e3ac2f75d48c50d415c4988b82792d1a
Reviewed-on: https://gerrit.instructure.com/36298
Reviewed-by: Jason Madsen <jmadsen@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>