We decide to separe codes for SRP

So FireUpdater.java is CREATED in update package

src/main/java/model/update/FireUpdater.java

+package model.update;
+
+import model.Fire;
+import util.Position;
+
+import java.util.*;
+
+public class FireUpdater {
+    private Fire fire;
+
+    public FireUpdater(Fire fire) {
+        this.fire = fire;
+    }
+
+    public List<Position> updateFire(Map<Position, List<Position>> neighbors, Set<Position> mountainPositions) {
+        return fire.spreadFire(mountainPositions);
+    }
+}
+