docs/zh_CN: Adjust the number of characters per line in magic-number.rst to less...

docs/zh_CN: Adjust the number of characters per line in magic-number.rst to less than 40

The current lines are too long and unfriendly to developers who use
vim to read documents, especially on small monitors, so let's adjust
to less than 40 characters.

In addition, some translations were modified incidentally.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/b3c1b55a442280c583518c45495e5540d6797548.1700474235.git.siyanteng@loongson.cn