fix error when showing time limit for fabulous quizzes

fixes CNVS-12843

test plan:
  - as a teacher
    - create a quiz with a time limit
    - enable fabulous quizzes

  - as a teacher
    - view the quiz overview tab
    - the time limit should display correctly

  - as a student
    - view the quiz overview tab
    - the time limit should display correctly

Change-Id: Ibdc32b731c5ece94b8f9990a7d69e3500dec2524
Reviewed-on: https://gerrit.instructure.com/34792
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Reviewed-by: Jason Madsen <jmadsen@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>