To remove the assignment of HU to delivery:-
1) VL02N to open the delivery in question
2) Click on the pack icon to enter the packing screen
3) Click to select the HU to be removed from delivery and click on the "Delete assignment" button, then save the delivery.
Image may be NSFW.
Clik here to view.
BTW, it's not necessary to delete the HU, just delete the assignment.
