[Migration Guide] Clarify provider url change in subchapter Update External JMS Clients

Migration Guide contains subchapter "4.2.2. Update External JMS Clients". There is mention about required update of the PROVIDER_URL from remote://localhost:4447 to http-remoting://127.0.0.1:8080. This needs a little clarification.
If you are using EAP6 and migrate to EAP7 using migrate operation, you don`t need to change PROVIDER_URL and you can still do with remote://localhost:4447. However, if you use EAP7 default configuration (not EAP 6 configurations migrated to EAP7 using migrate operation), you need to use http-remoting://127.0.0.1:8080.