Goatjo Quest Hooks 1.0.8 killer-only fix

Fix:
- Death quest credit is now restricted to the actual DamageSource player/owner gathered from the killing hit.
- Removed the multi-credit death resolver path that also included direct entity owner, victim killCredit/lastHurtByPlayer, and NBT owner/caster/thrower matches.
- This stops previous attackers/non-killers from completing weekly kill quests such as Disaster Curses when someone else gets the kill.
- Recent-damage fallback still exists for edge cases where death source cannot identify a valid player/owner.

Install:
- Replace goatjo_quest_hooks-1.0.7 with this jar on the server.
- Client install is not required unless your pack requires all mods on both sides.
