fix: correction of UseListsAndMaps.java exercise 6 description

java/collections/use-map/src/main/java/it/unibo/collections/UseListsAndMaps.java

@@ -91,7 +91,7 @@ public static void main(final String... s) {
          * 6) Measure the performance of reading 1000 times an element whose
          * position is in the middle of the collection for both ArrayList and
          * LinkedList, using the collections of point 5. In order to measure
-         * times, use as example PerfTest.java.
+         * times, use as example TestPerformance.java.
          */
         time = System.nanoTime();
         for (int i = 0; i < READS; i++) {