CompatHelper: bump compat for DomainSets to 0.8, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the DomainSets package from 0.6, 0.7 to 0.6, 0.7, 0.8.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (97a41a4) to head (ac5cb38).
⚠️ Report is 12 commits behind head on master.

Additional details and impacted files

@@          Coverage Diff           @@
##           master    #219   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files          11      12    +1     
  Lines         856     917   +61     
======================================
- Misses        856     917   +61     

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