sum-of-multiples: update starter implementation

exercises/sum-of-multiples/src/main/java/SumOfMultiples.java

-public class SumOfMultiples {
-    
+class SumOfMultiples {
+
+    SumOfMultiples(int number, int[] set) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+    int getSum() {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
 }