Psalm has introduced a feature for detecting unused entries in the error baseline. This is useful for a baseline that is maintained along with the code because it tells the developer when the baseline starts to smell and needs to be regenerated.

However, we use the baseline differently: We generate the baseline on the fly in order to check if a PR introduces new errors. Failing on baseline entries that can be purged is not what we want in that case because a contributor cannot fix those errors.

Example for a Psalm run that failed because of unused baseline entries: https://github.com/symfony/symfony/actions/runs/5706412328/job/15462071408