Gets some of the easy-bad species procs (#78993)

## About The Pull Request

- Kills `spec_death`, everything that used it is now signalized. 
- Kills `spec_hitby`, nothing used it. Anything that did hypothetically
can use the signal.

- [x] I tested this PR

## Why It's Good For The Game

These are all bad and using signals is superior. 

## Changelog

🆑 Melbert
code: Removed species death and species hitby, replaced any uses with
signals.
/🆑

code/modules/zombie/organs.dm

@@ -37,10 +37,22 @@
 	if(timer_id)
 		deltimer(timer_id)
 
+/obj/item/organ/internal/zombie_infection/on_insert(mob/living/carbon/organ_owner, special)
+	. = ..()
+	RegisterSignal(organ_owner, COMSIG_LIVING_DEATH, PROC_REF(organ_owner_died))
+
+/obj/item/organ/internal/zombie_infection/on_remove(mob/living/carbon/organ_owner, special)
+	. = ..()
+	UnregisterSignal(organ_owner, COMSIG_LIVING_DEATH)
+
+/obj/item/organ/internal/zombie_infection/proc/organ_owner_died(mob/living/carbon/source, gibbed)
+	SIGNAL_HANDLER
+	qdel(src) // Congrats you somehow died so hard you stopped being a zombie
+
 /obj/item/organ/internal/zombie_infection/on_find(mob/living/finder)
-	to_chat(finder, "<span class='warning'>Inside the head is a disgusting black \
+	to_chat(finder, span_warning("Inside the head is a disgusting black \
 		web of pus and viscera, bound tightly around the brain like some \
-		biological harness.</span>")
+		biological harness."))
 
 /obj/item/organ/internal/zombie_infection/process(seconds_per_tick, times_fired)
 	if(!owner)