Use new util function to find kernel specs

[ptsavol]

Re spine-tools/Spine-Toolbox#2824

Checklist before merging

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

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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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