docs/zh_cn: Fix a couple of reference warnings

Just put in the relevant file names and let automarkup handle the rest.

Fixes: 550c8399 ("docs/zh_CN: Add zh_CN/admin-guide/README.rst")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>