You cannot update a WebExtensions add-on with a legacy add-on. Your users would not be able to use your new version because Firefox does not support this type of update.
Ur tezmired ara ad tsemselsiḍ azegrir WebExtensions s uzegrir aqbuṛ. Iseqdacen inek ur ttizmiren ara ad sqedcen lqem amaynut acku Firefox ur isefrak ara anaw-agi n uleqqem.