Check if there are any EE specific Group relations that need export

With introduction of new group specific import_export.yml that specifies which relations to export there might be EE specific relations that need exporting, too.

Check and add these relations to group/import_export.yml, if necessary. Similar to project's import_export.yml https://gitlab.com/gitlab-org/gitlab/blob/master/lib%2Fgitlab%2Fimport_export%2Fimport_export.yml