fdo#72420 Startcenter: help button point to local/wiki help, ui part

Not handle clicking help button manually but use the defualt gtk-help
which will point to the corresponding help file depend
on helpids.

(cherry picked from commit 55fcca64a7d006f8cb10268fd2e1e09b1618a800)

Change-Id: I7ac4b51868d1a5828c810b1ac629d5a56ffb6f50
Reviewed-on: https://gerrit.libreoffice.org/7394
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>