unused ever since

    commit c1758889
    Date:   Fri Nov 11 22:48:37 2011 +0100
    Heavily simplified utl::ConfigManager.

and rename ConfigItemMode::ImmediateUpdate to NONE, since it doesn't
mean that anymore

Change-Id: Ia1d06142a25c9eea0f1d30b70653eed325a21b37
Reviewed-on: https://gerrit.libreoffice.org/64719
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>