Improve HIG for Calc Expon. Smoothing .ui

Change-Id: Ia935724c95c0ef3c5738c03ddc19f75f1838a753
Reviewed-on: https://gerrit.libreoffice.org/10694
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>