remove namespace from CSS class for quiz module items

fixes CNVS-12357

test plan:
- test the following with draft state off and on:
 1. create a practice quiz and a graded quiz
 2. add both to a module. do not reload the page afterward!
  a. both quiz items should have a 'Q' icon, not a document icon.
  b. edit the module. you should be able to add completion
     requirements for both items.
   i.  both quizzes should be in the 'Quizzes' category in the
       Add Requirement list.
   ii. the correct requirement types should be selectable
       (e.g., everything except "contribute to the page")
 3. add both quizzes to another module
 4. reload the page and repeat step 2 against the new
    module created in step 3

note that this commit reverts g/32966 and re-fixes the bug
refs CNVS-12052

Change-Id: I81ce696320c95e9ed31cde164588a96eda6d7a19
Reviewed-on: https://gerrit.instructure.com/34096
QA-Review: Clare Strong <clare@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jason Madsen <jmadsen@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>