Hide newquizzes_on_quiz_page feature flag
Hide newquizzes_on_quiz_page feature flag

closes QUIZ-7016

Test Plan
---------
- newquizzes_on_quiz_page feature flag is shown as 'hidden' for site
admins
- newquizzes_on_quiz_page feature flag is not shown to anyone other than
site admins

Change-Id: Ie56fcc51fd4ed732f2b28b49eb8c430a6def6eda
Reviewed-on: https://gerrit.instructure.com/211216
Tested-by: Jenkins
Reviewed-by: Alex Slaughter <11669a22a05ead38ed9badafd55ef4c5386724b6@instructure.com>
QA-Review: Tyler Burraston <be99835de7253fed1800dc291f72abb4f0d3c8dd@instructure.com>
Product-Review: Tyler Burraston <be99835de7253fed1800dc291f72abb4f0d3c8dd@instructure.com>

sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms