Decreases the TC-cost of shotgun slugs (#22563)

Shotguns are very cool but they sadly do not perform that well.

Shotguns are overshadowed by all other weapon types (SMGs, ARs and even
some pistols), and the only viable ammunition that makes shotguns viable
(slugs) is incredibly expensive to get as an antag.

This PR adds a new ammunition box to the uplink that includes 8 slugs
for only 2 TC, and also reduces the TC cost of the assault shotgun's
magazines to more reasonable amounts.

---------

Co-authored-by: bovvv <kavbest11@gmail.com>

code/datums/uplink/ammunition.dm

@@ -123,11 +123,11 @@
 	path = /obj/item/ammo_magazine/super_heavy
 	desc = "A spare magazine, for the super heavy K2557 pistol."
 
-/datum/uplink_item/item/ammo/shotgun_slug
-	name = "Shotgun Slug"
-	telecrystal_cost = 1
-	path = /obj/item/ammo_casing/shotgun
-	desc = "A shotgun slug."
+/datum/uplink_item/item/ammo/shotgun_slugs
+	name = "Box of Slug Shells"
+	telecrystal_cost = 2
+	path = /obj/item/storage/box/shells/slugs
+	desc = "Contains eight shotgun slug shells."
 
 /datum/uplink_item/item/ammo/tungsten_ammo_box
 	name = "Tungsten Ammo Box"
@@ -137,13 +137,13 @@
 
 /datum/uplink_item/item/ammo/slug_magazine
 	name = "Slug Magazine"
-	telecrystal_cost = 8
+	telecrystal_cost = 2
 	path = /obj/item/ammo_magazine/assault_shotgun
 	desc = "A magazine for an assault shotgun, loaded with slug shells."
 
 /datum/uplink_item/item/ammo/buckshot_magazine
 	name = "Buckshot Magazine"
-	telecrystal_cost = 4
+	telecrystal_cost = 1
 	path = /obj/item/ammo_magazine/assault_shotgun/shells
 	desc = "A magazine for an assault shotgun, loaded with buckshot shells."