Fix event type to avoid overlap with another decay file

There was unfortunate overlap with another decay file available only in Sim10 and not spotted when released. There are no events in bookkeeping with this decay file and here I'm fixing its event type to be unique (other decay file is older and has events in bookkeeping, so keeping that one untouched).

@fmangane, I will merge this asap and pick it up also in Sim10, but you need to wait until next release is announced later this week before preparing new request.