docs/zh_CN: Add secrets index Chinese translation

Translate .../security/secrets/index.rst into Chinese

Update the translation through commit 7419995a
("docs: security: Add secrets/coco documentation")

Signed-off-by: zhangwei <zhangwei@cqsoftware.com.cn>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/57978b69f643c1aacf78804affde4c819960fd3c.1738923258.git.zhangwei@cqsoftware.com.cn