[Fixes #13100] Fixing permissions bug of the delete_thumbnail endpoint

[Gpetrak]

This PR fixes this issue: #13100

Checklist

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.81%. Comparing base (de19f5e) to head (1c17dd4).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #13101   +/-   ##
=======================================
  Coverage   67.81%   67.81%           
=======================================
  Files         979      979           
  Lines       57453    57465   +12     
  Branches     6631     6632    +1     
=======================================
+ Hits        38962    38972   +10     
- Misses      16923    16926    +3     
+ Partials     1568     1567    -1     

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