remove final from class declaration in queen-attack exercise

exercises/queen-attack/src/main/java/BoardCoordinate.java

@@ -1,4 +1,4 @@
-public final class BoardCoordinate {
+public class BoardCoordinate {
 
 
 

exercises/queen-attack/src/main/java/QueenAttackCalculator.java

@@ -1,4 +1,4 @@
-public final class QueenAttackCalculator {
+public class QueenAttackCalculator {