makes w_class use defines (#9848)

code/modules/recycling/conveyor2.dm

@@ -291,7 +291,7 @@
 	icon_state = "conveyor0"
 	name = "conveyor belt assembly"
 	desc = "A conveyor belt assembly."
-	w_class = 4
+	w_class = ITEMSIZE_LARGE
 	var/id = "" //inherited by the belt
 
 /obj/item/conveyor_construct/attackby(obj/item/I, mob/user, params)
@@ -322,7 +322,7 @@
 	desc = "A conveyor control switch assembly."
 	icon = 'icons/obj/recycling.dmi'
 	icon_state = "switch-off"
-	w_class = 4
+	w_class = ITEMSIZE_LARGE
 	var/id = "" //inherited by the switch
 
 /obj/item/conveyor_switch_construct/New()

code/modules/recycling/sortingmachinery.dm

@@ -238,7 +238,7 @@
 	icon_state = "dest_tagger"
 	var/currTag = 0
 	matter = list(DEFAULT_WALL_MATERIAL = 250, MATERIAL_GLASS = 140)
-	w_class = 2
+	w_class = ITEMSIZE_SMALL
 	item_state = "electronic"
 	flags = CONDUCT
 	slot_flags = SLOT_BELT