BUILDENG-7877 Added autorequire for repository groups

Repository groups can contain both nexus_repository and nexus_repository_group types. We have only set up the autorequire relationship for nexus_repository. Adding one for nexus_repository_group is just as important.

For those not familiar with autorequire, (it sets up a 'soft' require relationship)[https://docs.puppetlabs.com/guides/custom_types.html#automatic-relationships] between resource and the defined resources of the type given as an argument to autorequire.