This menu doesn't have an effect on the importing while in the "Current File"
asset library. This can be quite confusing.
However, just hiding the menu may be a temporary solution. Decision
actually to instead show a different menu, that allows choosing between
duplicating and reusing data on drop. This is being reviewed here
https://developer.blender.org/D12879.
Meanwhile (or in case we end up rejecting that), this change should
avoid some confusion.
Differential Revision: https://developer.blender.org/D12752
4ba7201546