since we're replacing it completely anyhow.

which means we can remove DisconnectFromModel

Change-Id: I2f31d93eb95a641f3364d715111e70817c7e5087
Reviewed-on: https://gerrit.libreoffice.org/56849
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>