Review role-decoder and http-authentication-factory configuraiton in Elytron Subsystem Doc

Review and adjust role-decoder and http-authentication-factory in https://github.com/wildfly/wildfly/blob/main/docs/src/main/asciidoc/_elytron/Using_the_Elytron_Subsystem.adoc

From Farah:

if sections of the Docs add a role-decoder for Roles or configure an http-authentication-factory where a security-domain could be referenced instead

cc fjuma1@redhat.com