docs/zh_CN: fix links failure in license-rules

rST doc uses backquote `` to mark a link, which need a space before
and after the backquote sign in Chinese docs. Otherwise the link will be
translated as common context.

Use this patch to highlight this request.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Harry Wei <harryxiyou@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>