Move repositories reference for each module to settings.xml

As described here https://community.jboss.org/wiki/MavenGettingStarted-Developers , we should remove respositories definition from modules root poms and encourage people to use settings.xml instead.
We'll probably need to update CI jobs to have those respositories in their settings.xml, but I think it is already the case.
We'll need to update that page consequently: https://community.jboss.org/wiki/HowToBuildJBossToolsWithMaven3