CompatHelper: bump compat for ComplexityMeasures to 3, (keep existing compat)

This pull request changes the compat entry for the `ComplexityMeasures` package from `~3.7` to `~3.7, 3`. 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.