refactor: added code example for rules auto-replacement in creature's ETB (related to #12791)

Mage/src/main/java/mage/abilities/TriggeredAbilityImpl.java

@@ -132,6 +132,11 @@ public abstract class TriggeredAbilityImpl extends AbilityImpl implements Trigge
         return this;
     }
 
+    @Override
+    public String getTriggerPhrase() {
+        return this.triggerPhrase;
+    }
+
     @Override
     public void setTriggerEvent(GameEvent triggerEvent) {
         this.triggerEvent = triggerEvent;