Add private constructor to StatsViewer

Author: hazefully

fdb-record-layer-core/src/main/java/com/apple/foundationdb/record/query/plan/cascades/debug/StatsViewer.java

@@ -44,7 +44,11 @@
  * </p>
  */
 @SuppressWarnings("unused")
-public class StatsViewer {
+public final class StatsViewer {
+    private StatsViewer() {
+
+    }
+
     public static String showStats(@Nonnull final StatsDebugger statsDebugger) {
         final var statsMaps = statsDebugger.getStatsMaps();