Rename queen-attack starter class

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

@@ -0,0 +1,5 @@
+public final class BoardCoordinate {
+
+
+
+}

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

@@ -1,5 +0,0 @@
-public final class Coordinate {
-
-
-
-}