Adds One Shot RPG to Black Market (shiptest-ss13#3468)

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## About The Pull Request
as title
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## Why It's Good For The Game
Purchasable Anti-Armor for crews that might not otherwise have access to
it.
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## Changelog

:cl:
add: A cargo ship happened to lose an entire crate of Hammer Rocket
Launchers while travelling through the system. We have reason to believe
they're probably on sale now.
del: you can no longer purchase PML-9s on the black market.
/:cl:

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code/modules/cargo/blackmarket/blackmarket_items/explosives.dm

@@ -97,18 +97,6 @@
 	stock_max = 7
 	availability_prob = 50
 
-/datum/blackmarket_item/explosive/rpg
-	name = "PML-9 RPG"
-	desc = "Offically, it's an anti-armor RPG launcher. Technically, it's anti-everything. Most things don't enjoy being hit in the face with high explosives."
-	item = /obj/item/gun/ballistic/rocketlauncher
-
-	price_min = 3500
-	price_max = 6500
-	stock_min = 2
-	stock_max = 5
-	availability_prob = 10
-	spawn_weighting = FALSE
-
 /datum/blackmarket_item/explosive/live_bomb
 	name = "Active ICW Era Ordinance"
 	desc = "Look, I won't mince words. This thing is counting down and I don't want to be the next causualty of ICW after it's already ended. I'll sell it to you real cheap."

code/modules/cargo/blackmarket/blackmarket_items/weapons.dm

@@ -359,3 +359,14 @@
 	price_max = 3500
 	stock = 2
 	availability_prob = 40
+
+/datum/blackmarket_item/weapon/oneshot
+	name = "Hammer Launcher"
+	desc = "A one-shot solution to a myriad amount of problems, ranging from Exosuits to obnoxious neighbors. Contains one ready-to-fire 84mm HEDP rocket. "
+	item = /obj/item/gun/ballistic/rocketlauncher/oneshot
+
+	price_min = 3000
+	price_max = 4500
+	stock_min = 1
+	stock_max = 5
+	availability_prob = 25