Fix QuizGroup's course_id

[dgwn]

Proposed Changes

• QuizGroup fixed to have course_id of the quiz's course_id, instead of the quiz_id

Fixes #712.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (37639e6) to head (1cbfa66).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop      #713   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           75        75           
  Lines         3803      3803           
=========================================
  Hits          3803      3803           

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[Thetwam]

Thanks!