Fix fdo#80338 Help pages for Data Statistics

This is a text to get a mimnimum help for Calc Data Statistics.
It can be improved with better english and better maths.

Change-Id: I3771ed89c560df1e4e23835f5a15d8cfc47282cd
Reviewed-on: https://gerrit.libreoffice.org/11051
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>