VERDE: passa iterablePlayerTest

src/main/java/it/unimi/di/sweng/briscola/Player.java

@@ -88,6 +88,6 @@ public class Player implements Iterable<Card>{
   @NotNull
   @Override
   public Iterator<Card> iterator() {
-    return null;
+    return Collections.unmodifiableList(cards).iterator();
   }
 }