This workflow is also used on web sites and web sections.

Usually, we never delete data in ERP5, but keeping old categories and
old websections are sometimes a problem, because tegories and web
sections' IDs have a meaning.

Expired state already provides similar functionality that the deleted
state we usually have on workflows.

It's anyway "possible" to delete: Managers just switch to ZMI to delete,
non managers use "cut and paste" trick.

( see also comments in scripts/deleteDocument )