makes w_class use defines (#9848)

code/game/objects/items/weapons/storage/secure.dm

@@ -23,8 +23,8 @@
 	var/l_hacking = 0
 	var/emagged = 0
 	var/open = 0
-	w_class = 3
-	max_w_class = 2
+	w_class = ITEMSIZE_NORMAL
+	max_w_class = ITEMSIZE_SMALL
 	max_storage_space = 14
 	use_sound = 'sound/items/storage/briefcase.ogg'
 
@@ -154,7 +154,7 @@
 	force = 8.0
 	throw_speed = 1
 	throw_range = 4
-	w_class = 4.0
+	w_class = ITEMSIZE_LARGE
 
 	attack_hand(mob/user as mob)
 		if ((src.loc == user) && (src.locked == 1))
@@ -181,8 +181,8 @@
 	icon_locking = "safeb"
 	icon_sparking = "safespark"
 	force = 8.0
-	w_class = 8.0
-	max_w_class = 8
+	w_class = ITEMSIZE_IMMENSE
+	max_w_class = ITEMSIZE_IMMENSE
 	anchored = 1.0
 	density = 0
 	cant_hold = list(/obj/item/storage/secure/briefcase)