github: run unit tests on fedora:latest

[bboozzoo]

Use the latest stable Fedora image for unit tests.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.96%. Comparing base (96ea7b0) to head (cc3412a).
Report is 28 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #14684      +/-   ##
==========================================
+ Coverage   78.95%   78.96%   +0.01%     
==========================================
  Files        1084     1085       +1     
  Lines      146638   147109     +471     
==========================================
+ Hits       115773   116164     +391     
- Misses      23667    23719      +52     
- Partials     7198     7226      +28     

Flag	Coverage Δ
unittests	78.96% <ø> (+0.01%)	⬆️

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