I would notify the dispensary out of courtesy.

Anytime you change caregivers, you should notify the one you have now. That way he/she knows you are moving on and they can deal with the plant count as needed to stay within the law.

NOT telling your current caregiver that you plan to switch could leave them hanging in the breeze if the authorities show up and they are over on the plant count. Best to tell the grower so they can dispose of plants if necessary to stay within the limits.