"Show details" leaves matching q. matches intact

Closes CNVS-5608

TEST PLAN
---- ----

  - create a quiz with a matching question and a bunch of matches
  - save it and then go back to edit page
    + click on questions tab
    + click on "Show question details"
    + verify you still see the "Correct Answer" arrows
    + click on the 'edit question' little icon
      - verify the input boxes for the match texts are not prepended by
        "Correct Answer" like shown in the screencast
  - take the quiz by a student, get at least 1 match wrong, hand it in,
    and watch the quiz results page:
    + verify you see the "Correct Answer" arrow in the right place

Change-Id: I92696cbdc988fb3b36130afd87e7e957a7f34c4e
Reviewed-on: https://gerrit.instructure.com/41238
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Ryan Taylor <rtaylor@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Matt Fairbourn <mfairbourn@instructure.com>