CompatHelper: bump compat for DimensionalData to 0.27 for package ArviZSampleChainsExt, (keep existing compat)

[github-actions[bot]]

This pull request changes the compat entry for the DimensionalData package from 0.24, 0.25, 0.26 to 0.24, 0.25, 0.26, 0.27 for package ArviZSampleChainsExt. 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.