remove the rubric tab from ember quizzes#show

fixes CNVS-12575

test plan:
  - turn on fabulous quizzes
  - view an individual quiz
  - there should no longer be a tab for 'rubric'

Change-Id: I13ede66ad8e21c0f873bac5811a0a5ca37369eb4
Reviewed-on: https://gerrit.instructure.com/33687
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Josh Simpson <jsimpson@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>