test: skip failing MiniZinc tests

[gdalle]

Temporary workaround for #303

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.39%. Comparing base (4789944) to head (8081e26).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #305       +/-   ##
===========================================
+ Coverage   53.71%   99.39%   +45.67%     
===========================================
  Files          20       20               
  Lines        2139     2145        +6     
===========================================
+ Hits         1149     2132      +983     
+ Misses        990       13      -977     

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