l10n: zh_CN.po: translate 1 new message (2211t0f0u)

Update translation for git v1.9-rc2.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
l10n: zh_CN.po: Disambiguation for rebase

Disambiguate the Chinese translation for "rebase", and update other
related entries.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>