chore: Update coveralls setup

[mikolajb]

What problem does this PR solve?:
It looks like coveralls didn't work flow a while, let's update the setup

Which issue(s) does this PR fix?:

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Checklist

• If the PR adds a version bump, ensure there is no breaking change in Licensing model (or NA).
• If a chart is changed or app configuration is significantly changed, the chart version is correctly incremented (so that apps are not automatically upgraded from a previous version of DKP).

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