scripts/sphinx-pre-install: fix Arch xelatex dependency

On Arch Linux, xelatex is installed in the texlive-xetex package.

Signed-off-by: Li Hua <lihua@email.com>
Link: https://lore.kernel.org/r/20240326104515.40346-1-lihua@email.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>