don't show rubric icons when tabbing through the page
don't show rubric icons when tabbing through the page

hide rubric icons when tabbing through speedgrader,
and when tabbing through the individual rubric page.

closes CNVS-16436

test plan:

test plan:
- Have a course with at least 1 student
- Create an assignment that has a rubric attached
  (does not matter if the rubric is being used for grading or not)
- Have a student submit to the assignment
- In Speedgrader, view the rubric and verify the "+", "X"
  and pencil icons are no longer present when tabbing through the table.
  Also verify the icons are not present when hovering over the table.
- View the individual page for the rubric (for example,
  /courses/1/rubrics/1)
- Verify the "+", "X" and pencil icons are no longer present
  when tabbing through the table, before clicking the 'Edit Rubric'
  button. Also verify the icons are not present when hovering over
  the table.
- Click the 'Edit Rubric' button. Verify the icons show up when
  tabbing through the table. Also verify the icons show up when
  hovering over the table.

Change-Id: Id6c14fea24b9ed4c96a4ec826970798366a876a8
Reviewed-on: https://gerrit.instructure.com/43420
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Josh Simpson <bfb4987b134a00f73d881fff5113b1d5fa1876bc@instructure.com>
QA-Review: Amber Taniuchi <ef4bfd1e6d278f6bc7d4a478f02be2cb9581a0a5@instructure.com>
Product-Review: Spencer Olson <7cc0890d6f1f70810a023e7173eca5724d6c8e49@instructure.com>

matematikk-mooc/canvas-lms,roxolan/canvas-lms,eCNAP/CANVAS,whalejasmine/canvas-lms,whalejasmine/canvas-lms,va7map/canvas-lms,ShreniiNepal/shrenii_lmp,wrdsb/canvas-lms,samuels410/greatlakes-lms,matematikk-mooc/canvas-lms,fronteerio/canvas-lms,AndranikMarkosyan/lms,wrdsb/canvas-lms,juoni/canvas-lms,eCNAP/CANVAS,efrj/canvas-lms,Jyaasa/canvas-lms,antoniuslin/canvas-lms,matematikk-mooc/canvas-lms,Jyaasa/canvas-lms,redconfetti/canvas-lms,efrj/canvas-lms,Rvor/canvas-lms,djbender/canvas-lms,redconfetti/canvas-lms,kyroskoh/canvas-lms,antoniuslin/canvas-lms,skmezanul/canvas-lms,grahamb/canvas-lms,sdeleon28/canvas-lms,skmezanul/canvas-lms,roxolan/canvas-lms,va7map/canvas-lms,samuels410/greatlakes-lms,sfu/canvas-lms,kyroskoh/canvas-lms,Rvor/canvas-lms,shidao-fm/canvas-lms,SwinburneOnline/canvas-lms,AndranikMarkosyan/lms,samuels410/greatlakes-lms,snehakachroo1/LSI_replica,djbender/canvas-lms,greyhwndz/canvas-lms,dgynn/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,kyroskoh/canvas-lms,AndranikMarkosyan/lms,sfu/canvas-lms,jay3126/canvas-lms,tgroshon/canvas-lms,whalejasmine/canvas-lms,juoni/canvas-lms,tgroshon/canvas-lms,leftplusrightllc/canvas-lms,djbender/canvas-lms,matematikk-mooc/canvas-lms,HotChalk/canvas-lms,narigone/canvas,instructure/canvas-lms,eCNAP/CANVAS,venturehive/canvas-lms,greyhwndz/canvas-lms,venturehive/canvas-lms,roxolan/canvas-lms,AndranikMarkosyan/lms,grahamb/canvas-lms,va7map/canvas-lms,skmezanul/canvas-lms,snehakachroo1/LSI_replica,SwinburneOnline/canvas-lms,utkarshx/canvas-lms,fronteerio/canvas-lms,ShreniiNepal/shrenii_lmp,antoniuslin/canvas-lms,grahamb/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,tgroshon/canvas-lms,ShreniiNepal/shrenii_lmp,roxolan/canvas-lms,sdeleon28/canvas-lms,instructure/canvas-lms,eCNAP/CANVAS,sdeleon28/canvas-lms,whalejasmine/canvas-lms,tgroshon/canvas-lms,narigone/canvas,narigone/canvas,instructure/canvas-lms,snehakachroo1/LSI_replica,Jyaasa/canvas-lms,snehakachroo1/LSI_replica,utkarshx/canvas-lms,HotChalk/canvas-lms,shidao-fm/canvas-lms,Rvor/canvas-lms,sfu/canvas-lms,efrj/canvas-lms,jay3126/canvas-lms,SwinburneOnline/canvas-lms,instructure/canvas-lms,skmezanul/canvas-lms,efrj/canvas-lms,jay3126/canvas-lms,SwinburneOnline/canvas-lms,redconfetti/canvas-lms,wrdsb/canvas-lms,HotChalk/canvas-lms,dgynn/canvas-lms,samuels410/greatlakes-lms,kyroskoh/canvas-lms,antoniuslin/canvas-lms,leftplusrightllc/canvas-lms,greyhwndz/canvas-lms,fronteerio/canvas-lms,juoni/canvas-lms,juoni/canvas-lms,HotChalk/canvas-lms,venturehive/canvas-lms,leftplusrightllc/canvas-lms,grahamb/canvas-lms,shidao-fm/canvas-lms,utkarshx/canvas-lms,venturehive/canvas-lms,jay3126/canvas-lms,shidao-fm/canvas-lms,sdeleon28/canvas-lms,dgynn/canvas-lms,fronteerio/canvas-lms,narigone/canvas,redconfetti/canvas-lms,va7map/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,Jyaasa/canvas-lms,greyhwndz/canvas-lms,Rvor/canvas-lms,utkarshx/canvas-lms,instructure/canvas-lms,leftplusrightllc/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,ShreniiNepal/shrenii_lmp,wrdsb/canvas-lms