hide feature flag for multiple grading periods
hide feature flag for multiple grading periods

hide 'multiple grading periods' feature flag
for everybody except site-admins.

closes CNVS-16985
Change-Id: Ibd04232c3a9fb7131167ae5e30dcbc70d70c0168
Reviewed-on: https://gerrit.instructure.com/44618
Reviewed-by: Cameron Matheson <1d572acbfa68c7c6e541c7b840d6b622e5c0dc91@instructure.com>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
QA-Review: Spencer Olson <7cc0890d6f1f70810a023e7173eca5724d6c8e49@instructure.com>
Product-Review: Spencer Olson <7cc0890d6f1f70810a023e7173eca5724d6c8e49@instructure.com>

antoniuslin/canvas-lms,va7map/canvas-lms,va7map/canvas-lms,whalejasmine/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,roxolan/canvas-lms,sdeleon28/canvas-lms,Rvor/canvas-lms,HotChalk/canvas-lms,shidao-fm/canvas-lms,redconfetti/canvas-lms,samuels410/greatlakes-lms,SwinburneOnline/canvas-lms,roxolan/canvas-lms,tgroshon/canvas-lms,Rvor/canvas-lms,Rvor/canvas-lms,efrj/canvas-lms,shidao-fm/canvas-lms,utkarshx/canvas-lms,sdeleon28/canvas-lms,grahamb/canvas-lms,ShreniiNepal/shrenii_lmp,samuels410/greatlakes-lms,shidao-fm/canvas-lms,sfu/canvas-lms,fronteerio/canvas-lms,fronteerio/canvas-lms,venturehive/canvas-lms,wrdsb/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,kyroskoh/canvas-lms,roxolan/canvas-lms,fronteerio/canvas-lms,va7map/canvas-lms,kyroskoh/canvas-lms,tgroshon/canvas-lms,juoni/canvas-lms,leftplusrightllc/canvas-lms,wrdsb/canvas-lms,juoni/canvas-lms,sfu/canvas-lms,utkarshx/canvas-lms,wrdsb/canvas-lms,leftplusrightllc/canvas-lms,greyhwndz/canvas-lms,utkarshx/canvas-lms,sfu/canvas-lms,Jyaasa/canvas-lms,skmezanul/canvas-lms,jay3126/canvas-lms,shidao-fm/canvas-lms,HotChalk/canvas-lms,efrj/canvas-lms,wrdsb/canvas-lms,kyroskoh/canvas-lms,redconfetti/canvas-lms,skmezanul/canvas-lms,skmezanul/canvas-lms,antoniuslin/canvas-lms,djbender/canvas-lms,SwinburneOnline/canvas-lms,greyhwndz/canvas-lms,antoniuslin/canvas-lms,greyhwndz/canvas-lms,ShreniiNepal/shrenii_lmp,HotChalk/canvas-lms,efrj/canvas-lms,samuels410/greatlakes-lms,grahamb/canvas-lms,fronteerio/canvas-lms,leftplusrightllc/canvas-lms,Jyaasa/canvas-lms,roxolan/canvas-lms,greyhwndz/canvas-lms,Rvor/canvas-lms,kyroskoh/canvas-lms,juoni/canvas-lms,va7map/canvas-lms,grahamb/canvas-lms,whalejasmine/canvas-lms,leftplusrightllc/canvas-lms,redconfetti/canvas-lms,utkarshx/canvas-lms,HotChalk/canvas-lms,SwinburneOnline/canvas-lms,whalejasmine/canvas-lms,whalejasmine/canvas-lms,ShreniiNepal/shrenii_lmp,jay3126/canvas-lms,juoni/canvas-lms,Jyaasa/canvas-lms,tgroshon/canvas-lms,sdeleon28/canvas-lms,redconfetti/canvas-lms,grahamb/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,Jyaasa/canvas-lms,efrj/canvas-lms,tgroshon/canvas-lms,grahamb/canvas-lms,sfu/canvas-lms,sdeleon28/canvas-lms,jay3126/canvas-lms,venturehive/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,SwinburneOnline/canvas-lms,antoniuslin/canvas-lms,ShreniiNepal/shrenii_lmp,samuels410/greatlakes-lms,skmezanul/canvas-lms,jay3126/canvas-lms