When you’ve deleted an ODS/Infocube/Infoobject (aka target), without prior having deleted the update rule which was linked to that particular target, the update rule still ‘wanders around’ your SAP BI system. (Eventhough you can not see it via transaction RSA1)
You can deleted this (orphan) update rule (call it some kind of “garbage collection”) via function module ‘RSAU_UPDR_DELETE’. (tcode SE37 –> ‘RSAU_UPDR_DELETE’ )