do not replace a General format with a General format

Found when investigating fdo#79228 which was caused by the ScPatternAttr
change due to the number format being applied.

Change-Id: Ieada557f5e194401a9ce255f26d71d36e0704f35
(cherry picked from commit f68eed1518fe689fe8a535bebc8d2b6c9f257b9c)
Reviewed-on: https://gerrit.libreoffice.org/9511
Tested-by: Kohei Yoshida <libreoffice@kohei.us>
Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>