A11y: Make grade history links more accessible
A11y: Make grade history links more accessible

fixes CNVS-28205

Test plan:
- Visit Gradebook History
- Visually inspect the grade history toggle links for assignments.
- Verify that they appear as they did before this commit.
- Verify that screen readers read the text "grade history" after the
   assignment name

Change-Id: I4df51ed2f169a8760a917c9a9d9d2d5f4b119e7b
Reviewed-on: https://gerrit.instructure.com/75209
Reviewed-by: Cameron Matheson <1d572acbfa68c7c6e541c7b840d6b622e5c0dc91@instructure.com>
Tested-by: Jenkins
QA-Review: KC Naegle <9fbecd016338f9910821a8a5d5d0ae4fc9abfaa5@instructure.com>
Product-Review: Aaron Cannon <25919c673621c006b735dcd5a28df63325948e2b@instructure.com>

sfu/canvas-lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,roxolan/canvas-lms,venturehive/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,fronteerio/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,roxolan/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,grahamb/canvas-lms,dgynn/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,roxolan/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,SwinburneOnline/canvas-lms,dgynn/canvas-lms,grahamb/canvas-lms,fronteerio/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,HotChalk/canvas-lms,grahamb/canvas-lms,fronteerio/canvas-lms,HotChalk/canvas-lms,venturehive/canvas-lms,HotChalk/canvas-lms,djbender/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,HotChalk/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,SwinburneOnline/canvas-lms,matematikk-mooc/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms