After datalad dataset id convention was changed in 3590aca, the old IDs
remained in DataItems. This does the following replacement:
old - "part_of":"datalad:698cec3c-e424-47e0-9da4-7a75e5ed6078"
new - "part_of":"datalad:698cec3c-e424-47e0-9da4-7a75e5ed6078/dl/dataset"
AFAICS the TRR379DataItem still has the `part_of` slot with
TRR379Dataset range, so I am assuming this was just an ommission.