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

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.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

scripts/sphinx-pre-install

@@ -78,6 +78,7 @@ my %texlive = (
 	'ucs.sty'            => 'texlive-ucs',
 	'upquote.sty'        => 'texlive-upquote',
 	'wrapfig.sty'        => 'texlive-wrapfig',
+	'ctexhook.sty'       => 'texlive-ctex',
 );
 
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