the UnoDialog constructor parameters can be simplified

Change-Id: I5c790a4b79966c977899a0cdacde8fb41148eb1a
Reviewed-on: https://gerrit.libreoffice.org/13092
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>