HP Sling fix (shiptest-ss13#4167)

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## About The Pull Request
The:
- Flaming Arrow
- Conflagation
- Absolution
- Beacon
- Vickland

can have slings attached to them again.


![obraz](https://github.com/user-attachments/assets/8b7ac495-5788-46cc-9917-cccdafa30b19)

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## Why It's Good For The Game
I'm guessing it's an oversight from shiptest-ss13#3736
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## Changelog

:cl:
fix: Flaming Arrow, Conflagation, Absolution, Beacon and Vickland can
have shoulder slings attached to them again.
/:cl:

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code/modules/projectiles/guns/manufacturer/hunter_pride/ballistics.dm

@@ -698,6 +698,7 @@ EMPTY_GUN_HELPER(shotgun/flamingarrow/conflagration)
 		/obj/item/attachment/laser_sight,
 		/obj/item/attachment/rail_light,
 		/obj/item/attachment/bayonet,
+		/obj/item/attachment/sling,
 		/obj/item/attachment/scope,
 		/obj/item/attachment/long_scope,
 	)
@@ -854,6 +855,7 @@ EMPTY_GUN_HELPER(shotgun/flamingarrow)
 		/obj/item/attachment/laser_sight,
 		/obj/item/attachment/rail_light,
 		/obj/item/attachment/bayonet,
+		/obj/item/attachment/sling,
 		/obj/item/attachment/scope,
 		/obj/item/attachment/long_scope,
 	)
@@ -951,6 +953,7 @@ EMPTY_GUN_HELPER(shotgun/doublebarrel/beacon)
 		/obj/item/attachment/laser_sight,
 		/obj/item/attachment/rail_light,
 		/obj/item/attachment/bayonet,
+		/obj/item/attachment/sling,
 		/obj/item/attachment/scope,
 		/obj/item/attachment/long_scope,
 	)