Fix root pom override of hippo-cms7-release parent pom

The GoGreen shouldn't depend on an unreleased hippo-cms7-release-xxx-SNAPSHOT version until it is released, but instead override latest released version locally.
For dependency version overriding only version property definitions should be used, not include actual dependency (management) overrides themselves, unless it concerns a new artifact which hasn't been configured on the hippo-cms7-release parent pom yet.