doc/zh_CN: Clean zh_CN translation maintainer

doc/zh_CN: Clean zh_CN translation maintainer

Remove Harry Wei and <xiyoulinuxkernelgroup@googlegroups.com> from
MAINTAINERS Chinese Translation.

According to git logs, Harry Wei (aka WeiWei Jia)
* last submitted at 2012-05-07
commit a9e73211fb0f ("Fix a mistake sentence in the file 'Documentation/zh_CN/magic-number.txt'")
* last Reviewed-by at 2016-02-16
commit 45c73ea7a785 ("Documentation: Chinese translation of arm64/silicon-errata.txt")
* last Signed-off-by at 2019-03-13 (pick by Alex Shi)
commit 95dcdb6e125f ("docs/zh_CN: rename magic-numbers as rst doc")

According to mail list archives, Harry Wei
* last replied at 2016-02-15
<https://lore.kernel.org/lkml/CAD+1EGPFdoD7HHZYfEWVvmesXXG27n=6KmEZ8=B6nrvb+oaLZA@mail.gmail.com/>
* last appeared at 2018-05-12
<https://lore.kernel.org/lkml/CA+scX6kYH8Y9_f1PLcMHG-MD9bhXgd4gGpkJanjzvwwj9L=aOQ@mail.gmail.com/>

He/She did not maintain zh_CN translations for a long time.
<xiyoulinuxkernelgroup@googlegroups.com> is a maillist for Linux group of
Xi'an University of Posts and Telecommunications, not special for zh_CN
translation work.

Anyway, many thanks him/her and Xiyou for their contributions to the early
Chinese translation work!

Signed-off-by: Wu XiangCheng <bobwxc@email.cn>
Link: https://lore.kernel.org/r/20210329151551.GA10901@mipc
Signed-off-by: Jonathan Corbet <corbet@lwn.net>