member already present in superclass InheritedHelperInterfaceImpl

Change-Id: I52a8178f95ad65dc0780ba0f82d6322cea039ba4
Reviewed-on: https://gerrit.libreoffice.org/54109Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>