chore: remove gating on learner credit enrollment upgrades from Dashboard

[adamstankiewicz]

ENT-9135

Removes the gating (i.e., staff user or feature flag enabled via query parameter) on the API call to can-redeem within potentially upgradeable audit course enrollments.

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 87.09%. Comparing base (70d9015) to head (4bf12da).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1139      +/-   ##
==========================================
- Coverage   87.10%   87.09%   -0.01%     
==========================================
  Files         392      392              
  Lines        8165     8161       -4     
  Branches     2017     2009       -8     
==========================================
- Hits         7112     7108       -4     
  Misses       1003     1003              
  Partials       50       50              

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