Use new util function to find kernel specs

[ptsavol]

Re spine-tools/Spine-Toolbox#2824

Checklist before merging

• Release notes in Toolbox repo have been updated
• Unit tests have been added/updated accordingly
• Code has been formatted by black
• Unit tests pass

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.36%. Comparing base (4f8d629) to head (5e4df41).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #213      +/-   ##
==========================================
- Coverage   62.37%   62.36%   -0.01%     
==========================================
  Files         168      168              
  Lines       17742    17741       -1     
  Branches     2951     2951              
==========================================
- Hits        11066    11065       -1     
  Misses       6074     6074              
  Partials      602      602              

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