Super stable bomb payloads actually don't blow up when burnt (#95053)

## About The Pull Request

Super stable bomb payloads aren't supposed to detonate when burnt, but
because making a subtype proc that calls parent does literally nothing
that wasn't the case.

I can't for the life of me remember a way to call two parents down, so
it's just a check on `/obj/item/bombcore/burn()`.

## Why It's Good For The Game

"Super-stable" my ass
This was already supposed to be the case, as evidenced by both its
description & the code comment above it.

## Changelog
🆑

fix: The "Super-Stable" line of Donk Co. Bomb Payloads are now stable
when exposed to extreme temperatures

/🆑

code/game/machinery/syndicatebomb.dm

@@ -363,13 +363,16 @@
 	var/range_medium = 9
 	var/range_light = 17
 	var/range_flame = 17
+	/// Whether this core explodes when burnt
+	var/explodes_when_burnt = TRUE
 
 /obj/item/bombcore/ex_act(severity, target) // Little boom can chain a big boom.
 	detonate()
 	return TRUE
 
 /obj/item/bombcore/burn()
-	detonate()
+	if(explodes_when_burnt)
+		detonate()
 	..()
 
 /obj/item/bombcore/proc/detonate()
@@ -390,13 +393,11 @@
 /obj/item/bombcore/syndicate
 	name = "Donk Co. Super-Stable Bomb Payload"
 	desc = "After a string of unwanted detonations, this payload has been specifically redesigned to not explode unless triggered electronically by a bomb shell."
+	explodes_when_burnt = FALSE
 
 /obj/item/bombcore/syndicate/ex_act(severity, target)
 	return FALSE
 
-/obj/item/bombcore/syndicate/burn()
-	return ..()
-
 /obj/item/bombcore/syndicate/large
 	name = "Donk Co. Super-Stable Bomb Payload XL"
 	range_heavy = 5