Update thing-xml.md reduce code example to one liner (#961)

Signed-off-by: Christoph Weitkamp <github@christophweitkamp.de>

developers/bindings/thing-xml.md

@@ -382,9 +382,7 @@ public class ExampleDynamicCommandDescriptionProvider implements DynamicCommandD
             return null;
         }
 
-        CommandDescriptionBuilder builder = CommandDescriptionBuilder.create();
+        return CommandDescriptionBuilder.create().withCommandOptions(options).build();
-        options.forEach(co -> builder.withCommandOption(co));
-        return builder.build();
     }
 }
 ```