Improve logging for datagroup generation fallback in CI

[scholtzan]

Currently, the logging for generating datagroups in CI can be confusing and should be improved. The dryrun account does not have permissions to dryrun certain tables, but when that happens it will pull the lookml file from looker-hub instead. So the CI doesn't actually fail in those cases. The logging however indicates that some error happened, which is confusing to users. Example: https://github.com/mozilla/lookml-generator/actions/runs/18914132824/job/53999330149?pr=1337

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