8331750: [11u] JDK-8259530 is not backported correctly to 11u

Reviewed-by: phh

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/formats/html/HtmlConfiguration.java

@@ -661,7 +661,7 @@ public boolean process(String opt,  List<String> args) {
                     return true;
                 }
             },
-            new Option(resources, "--legal-notices", 1) {
+            new XOption(resources, "--legal-notices", 1) {
                 @Override
                 public boolean process(String opt,  List<String> args) {
                     legalnotices = args.get(0);