fix: remove duplicative course run card on allocation

[brobro10000]

During the transition to run based assignments, a refactor was missed related to filtering out duplicative learner credit allocations on a potentially upgradable audit enrollment on the learner dashboard page. This did not affect the user's ability to upgrade their audit enrollment. It presented a confusing UI experience on which course card to proceed on (Upgrade or learner credit enrollment.)

This PR removes duplicative course cards by filtering on the course run vs the content key which may either be a top level course or a course run id.

Prior to fix:

After fix:

For all changes

• Ensure adequate tests are in place (or reviewed existing tests cover changes)
• Ensure English strings are marked for translation. See documentation for more details.

Only if submitting a visual change

• Ensure to attach screenshots
• Ensure to have UX team confirm screenshots

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.21%. Comparing base (a8094f0) to head (e63a5fc).
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1248      +/-   ##
==========================================
+ Coverage   89.00%   89.21%   +0.21%     
==========================================
  Files         403      405       +2     
  Lines        8733     8738       +5     
  Branches     2124     2064      -60     
==========================================
+ Hits         7773     7796      +23     
+ Misses        918      906      -12     
+ Partials       42       36       -6     

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