Ember quizzes now has the screenreader h1 element

Previously, the ember quizzes index page was lacking the h1
screenreader-only element needed for accessibility

Closes CNVS-14004

Test Plan:
  - Examine quizzes/:quiz/index and test that the h1 screenreader-only
 element is visible to the screen reader between the breadcrumbs and
 main content.

Change-Id: I63117dca4595d766d2545adde3817756cf3acedd
Reviewed-on: https://gerrit.instructure.com/40398
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Ryan Taylor <rtaylor@instructure.com>