Rock Planet Shipping Dock has the correct gun (shiptest-ss13#3545)

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## About The Pull Request

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Rock Planet shipping dock ruin has a rattlesnake instead of the ringneck
case.

![image](https://github.com/user-attachments/assets/24637f48-0658-4efd-9a57-446cb3b48e22)


## Why It's Good For The Game

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Seems like the ringneck got mapped in by mistake, since the crate had
two rattlesnake mags, and the gun there before was the TEC-9, which the
rattlesnake was supposed to replace.

## Changelog

:cl:
fix: Shipping dock ruin correctly has a rattlesnake instead of a
ringneck case
/:cl:

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_maps/RandomRuins/RockRuins/rockplanet_shippingdock.dmm

@@ -2002,7 +2002,7 @@
 	},
 /obj/item/ammo_box/magazine/m9mm_rattlesnake,
 /obj/item/ammo_box/magazine/m9mm_rattlesnake,
-/obj/item/storage/pistolcase/ringneck,
+/obj/item/gun/ballistic/automatic/pistol/rattlesnake/no_mag,
 /turf/open/floor/plasteel/mono/dark,
 /area/ruin/rockplanet/shippingdocksecure)
 "rK" = (