Provide Example Authentication Client Configuration in the wildfly-config.xml File in Development Guide

Book: Development Guide
Revision: c5ece0e
Section: 18.1.1. Client Authentication Configuration Using the wildfly-config.xml File

As part of fix JBEAP-10297 there was removed incorrect example Example Authentication Client Configuration in the wildfly-config.xml File at the end of section 18.1.1. Client Authentication Configuration Using the wildfly-config.xml File. However it should be rather rewritten to some correct example instead of completely removed.