resolved fdo#73836 do not apply format twice to string

ScDocument::GetString() already returns the formatted string that then
was formatted through number formatter. Format raw string instead.

Change-Id: I806b4fc904d04169a6c1dbd4a3d00e2556eda7bd
(cherry picked from commit f6b9b73a1f87d1815ed8ab8f2494e5526a710bb9)
Reviewed-on: https://gerrit.libreoffice.org/7549
Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>
Tested-by: Kohei Yoshida <libreoffice@kohei.us>