update zh-cn/device-dev/kernel/Readme-CN.md.

Signed-off-by: Nli-yan339 <liyan339@h-partners.com>
Signed-off-by: Nliyan <liyan339@h-partners.com>

zh-cn/device-dev/kernel/Readme-CN.md

-# kernel
+# 内核
 
-- 内核
     - [内核概述](kernel-overview.md)
     - 轻量系统内核（LiteOS-M）
         - [轻量系统内核概述](kernel-mini-overview.md)