scripts: sphinx-pre-install: add required ctex dependency

stable inclusion
from stable-v5.10.94
commit 133cef0b6154cf71202462bb2738dbadd62b8198
bugzilla: https://gitee.com/openeuler/kernel/issues/I531X9

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=133cef0b6154cf71202462bb2738dbadd62b8198



--------------------------------

commit 7baab965 upstream.

After a change meant to fix support for oriental characters
(Chinese, Japanese, Korean), ctex stylesheet is now a requirement
for PDF output.

Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lore.kernel.org/r/165aa6167f21e3892a6e308688c93c756e94f4e0.1641243581.git.mchehab@kernel.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>