add missing Integer.class

fixes #3459

Author: Vladimir Kotal

opengrok-indexer/src/main/java/org/opengrok/indexer/index/Indexer.java

@@ -618,7 +618,7 @@ public static String[] parseOptions(String[] argv) throws ParseException {
                     "files), but process all other command line options.").execute(v ->
                     runIndex = false);
 
-            parser.on("--nestingMaximum", "=number",
+            parser.on("--nestingMaximum", "=number", Integer.class,
                     "Maximum depth of nested repositories. Default is 1.").execute(v ->
                     cfg.setNestingMaximum((Integer) v));