fix(es_extended/server/classes/vehicle): update self.plate in setPlate

setPlate re-keys Core.vehicles but never updates self.plate, so the object
it was called on keeps pointing at the removed key. isValid() fails from
then on and every later call on that handle is a no-op, including delete(),
which leaves the vehicle spawned and owned_vehicles.stored at false.

[core]/es_extended/server/classes/vehicle.lua

@@ -154,6 +154,7 @@ Core.vehicleClass = {
 		vehicleData.plate = newPlate
 		Core.vehicles[newPlate] = table.clone(vehicleData)
 		Core.vehicles[oldPlate] = nil
+		self.plate = newPlate
 
 		TriggerEvent("esx:changedExtendedVehiclePlate", vehicleData.plate, oldPlate)
 		Wait(0)