OZG-6867 Remove adding subgroups to keycloak

src/main/java/de/ozgcloud/admin/keycloak/AddGroupData.java

...n/java/de/ozgcloud/admin/keycloak/KeycloakApiService.java

...dmin/organisationseinheit/OrganisationsEinheitMapper.java

...einheit/OrganisationsEinheitSynchronizationException.java

...a/de/ozgcloud/admin/organisationseinheit/SyncService.java

...a/de/ozgcloud/admin/keycloak/AddGroupDataTestFactory.java

...test/java/de/ozgcloud/admin/keycloak/GroupMapperTest.java

.../de/ozgcloud/admin/keycloak/KeycloakApiServiceITCase.java

...va/de/ozgcloud/admin/keycloak/KeycloakApiServiceTest.java

.../organisationseinheit/OrganisationsEinheitMapperTest.java

...sationseinheit/SyncAddedOrganisationsEinheitenITCase.java

.../ozgcloud/admin/organisationseinheit/SyncServiceTest.java