don't add the changes toolbar to the forms window, fdo#76752

Change-Id: I1a5d62b0995343a73fd8d6941f0fa380bb19e783
Reviewed-on: https://gerrit.libreoffice.org/9606
Reviewed-by: Eike Rathke <erack@redhat.com>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>