and remove reading/writing of defunct ExtraData from rsc

Change-Id: I5be6e11c5921eb809143487a456d1e4ee203e68c
Reviewed-on: https://gerrit.libreoffice.org/34345Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>