fix: error code expecting wrong data shape

[jansenk]

frontend was expecting gradeStatus lockStatus and gradeData to be wrapped in a submissionStatus object. They are not.

manual reproduction:

• Have the ora grading MFE installed locally and go to the grading for an ORA with at least one available submission
• Click "start Grading"
• Go to the LMS django admin page for submission grading locks
• change the user ID for the lock owner to some random string
• attempt to submit a grade

before change: page crashes, error about "iconAfter"
after change: error handled

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (f87d521) to head (ebca59a).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #390   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          109       109           
  Lines         1085      1085           
  Branches       165       165           
=========================================
  Hits          1085      1085           

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