"@Override" tag

Inadvertently removed in back/forward porting gymnastics.

src/main/java/org/apache/commons/math4/ml/neuralnet/twod/util/UnifiedDistanceMatrix.java

@@ -60,6 +60,7 @@ public class UnifiedDistanceMatrix implements MapVisualization {
     }
 
     /** {@inheritDoc} */
+    @Override
     public double[][] computeImage(NeuronSquareMesh2D map) {
         if (individualDistances) {
             return individualDistances(map);