Make metal briefcases sound metallic (#21673)

They had the same sound as a backpack before, which did not make sense
for something made of metal. This simply fixes that so it sounds
metallic, similar to toolboxes and the crime scene kit.

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

@@ -30,6 +30,9 @@
 	desc = "A heavy-duty briefcase for your most important documents."
 	icon_state = "briefcase_alum"
 	item_state = "briefcase_alum"
+	use_sound = 'sound/items/storage/toolbox.ogg'
+	drop_sound = 'sound/items/drop/toolbox.ogg'
+	pickup_sound = 'sound/items/pickup/toolbox.ogg'
 
 /obj/item/storage/briefcase/nt
 	name = "\improper NT briefcase"