Fix the instant kill effect not removing itself

src/game/combat/effects.ts

@@ -10,6 +10,7 @@ export class InstantKillEffect extends StatusEffect {
 
   onApply (creature: Creature) {
     creature.vigors.Health = 0
+    creature.removeEffect(this)
     return new LogLines(
       new LogLine(
         `${creature.name.capital} ${creature.name.conjugate(new ToBe())} killed instantly! `,