Remove visual noise from bridges

Change-Id: I53fa23d335ff62795f09f9838d4064cea71aeb65
Reviewed-on: https://gerrit.libreoffice.org/8237
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>