cubicweb #2788402 [dataimport] Alleviate the need to check for the input data format (see CS 3089d2aeaf10). [deprecated]

For now, the CS 3089d2aeaf10 on dataimport is needed, because the input data can be structured in different ways.

This problem should be handled before reading the data.

Thus, CS 3089d2aeaf10 should not be needed anymore, in the long run.

done in<not specified>
load left0.000
closed by<not specified>