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

Change-Id: I1a5d62b0995343a73fd8d6941f0fa380bb19e783
Reviewed-on: https://gerrit.libreoffice.org/9605
Reviewed-by: Maxim Monastirsky <momonasmon@gmail.com>
Tested-by: Maxim Monastirsky <momonasmon@gmail.com>