CI: Fix test coverage checks

[six7]

Our Test coverage steps are currently failing for most PRs. We should look into this and see if we can find improvements. Ideally we'd easily see which files are causing a drop in coverage, and by how much

Set up test coverage step to be closer to what we do for style dictionary and provide no false positives, see https://hyma-team.slack.com/archives/C03BSF3TADU/p1716463210584889