Fixes a broken path on the black market (tgstation#81942)

## About The Pull Request

We have a misspelled path here for a black market fish case, which is
creating a broken object called `fish_cas`

## Why It's Good For The Game

🐛 💥 Fixes a rather basic path bug that I came across, simple as.

## Changelog

:cl:
fix: The black market illegal fish case now correctly initializes.
/:cl:

code/modules/fishing/aquarium/aquarium_kit.dm

@@ -85,7 +85,7 @@
 	)
 	return pick_weight(weighted_list)
 
-/obj/item/storage/fish_cas/blackmarket/Initialize(mapload)
+/obj/item/storage/fish_case/blackmarket/Initialize(mapload)
 	. = ..()
 	for(var/obj/item/fish/fish as anything in contents)
 		fish.set_status(FISH_DEAD)