remove reference to missing plugins css package
remove reference to missing plugins css package

fixes CNVS-12836

test plan:
- visit the plugins index

Change-Id: Ie37dbc5ef5f1f00860b9071c21ec49c5fc852d1c
Reviewed-on: https://gerrit.instructure.com/34261
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
QA-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

fronteerio/canvas-lms,wye0220/shindig-canvas,juoni/canvas-lms,Rvor/canvas-lms,Jyaasa/canvas-lms,redconfetti/canvas-lms,sfu/canvas-lms,antoniuslin/canvas-lms,utkarshx/canvas-lms,venturehive/canvas-lms,Jyaasa/canvas-lms,sfu/canvas-lms,tgroshon/canvas-lms,samuels410/greatlakes-lms,efrj/canvas-lms,leftplusrightllc/canvas-lms,leftplusrightllc/canvas-lms,wrdsb/canvas-lms,leftplusrightllc/canvas-lms,roxolan/canvas-lms,kyroskoh/canvas-lms,venturehive/canvas-lms,samuels410/greatlakes-lms,sfu/canvas-lms,utkarshx/canvas-lms,jay3126/canvas-lms,sdeleon28/canvas-lms,fronteerio/canvas-lms,whalejasmine/canvas-lms,kyroskoh/canvas-lms,HotChalk/canvas-lms,HotChalk/canvas-lms,sdeleon28/canvas-lms,usmschuck/canvas,Unow/canvas-lms,djbender/canvas-lms,ShreniiNepal/shrenii_lmp,venturehive/canvas-lms,Jyaasa/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,SwinburneOnline/canvas-lms,antoniuslin/canvas-lms,skmezanul/canvas-lms,samuels410/greatlakes-lms,shidao-fm/canvas-lms,HotChalk/canvas-lms,antoniuslin/canvas-lms,djbender/canvas-lms,kyroskoh/canvas-lms,grahamb/canvas-lms,redconfetti/canvas-lms,Unow/canvas-lms,tgroshon/canvas-lms,skmezanul/canvas-lms,ShreniiNepal/shrenii_lmp,greyhwndz/canvas-lms,efrj/canvas-lms,whalejasmine/canvas-lms,Rvor/canvas-lms,wrdsb/canvas-lms,sdeleon28/canvas-lms,samuels410/greatlakes-lms,sfu/canvas-lms,roxolan/canvas-lms,juoni/canvas-lms,SwinburneOnline/canvas-lms,Unow/canvas-lms,roxolan/canvas-lms,usmschuck/canvas,va7map/canvas-lms,wye0220/shindig-canvas,grahamb/canvas-lms,HotChalk/canvas-lms,ShreniiNepal/shrenii_lmp,juoni/canvas-lms,Rvor/canvas-lms,efrj/canvas-lms,jay3126/canvas-lms,djbender/canvas-lms,juoni/canvas-lms,Jyaasa/canvas-lms,jay3126/canvas-lms,ShreniiNepal/shrenii_lmp,jay3126/canvas-lms,roxolan/canvas-lms,grahamb/canvas-lms,venturehive/canvas-lms,grahamb/canvas-lms,utkarshx/canvas-lms,wye0220/shindig-canvas,grahamb/canvas-lms,djbender/canvas-lms,va7map/canvas-lms,redconfetti/canvas-lms,greyhwndz/canvas-lms,greyhwndz/canvas-lms,utkarshx/canvas-lms,wrdsb/canvas-lms,redconfetti/canvas-lms,SwinburneOnline/canvas-lms,usmschuck/canvas,shidao-fm/canvas-lms,kyroskoh/canvas-lms,skmezanul/canvas-lms,whalejasmine/canvas-lms,usmschuck/canvas,shidao-fm/canvas-lms,shidao-fm/canvas-lms,antoniuslin/canvas-lms,leftplusrightllc/canvas-lms,va7map/canvas-lms,whalejasmine/canvas-lms,efrj/canvas-lms,SwinburneOnline/canvas-lms,tgroshon/canvas-lms,sdeleon28/canvas-lms,sfu/canvas-lms,fronteerio/canvas-lms,Rvor/canvas-lms,skmezanul/canvas-lms,greyhwndz/canvas-lms,va7map/canvas-lms,tgroshon/canvas-lms,sfu/canvas-lms,wrdsb/canvas-lms