Storing Undo data is unnecessary here, because shrinking is applied
only on the  text frame of the textbox. The shape component of the
textbox isn't modified.

(cherry-picked from 2f779fc0)

Change-Id: Iaff64ff4953adbfa830832da146343cef2734547
Reviewed-on: https://gerrit.libreoffice.org/16088Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>