use the same setting as the emoji popover so that at the top of a dialog the
popover pops down and at the bottom of a dialog is pops up.

Change-Id: I8e6cd13c5f669b5218c65096f68471bf2e27c848
Reviewed-on: https://gerrit.libreoffice.org/56483
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>