Update Multi-Project Build Guide with Development Reloading Information

[jamesfredley]

Issue description

https://guides.grails.org/grails-multi-project-build/guide/index.html

Adjust based on #14977

[jamesfredley]

This issue will stay until a Grails 7 version of the Guide: https://guides.grails.org/grails-multi-project-build/guide/index.html with the minor new details is published.

[jdaugherty]

Thanks @jamesfredley , I misread this was for the guide and not the documentation.