docs/doc-guide: Clarify how to write tables

docs/doc-guide: Clarify how to write tables

Prior to this commit, the kernel docs writing guide spent over a page
describing exactly how *not* to write tables into the kernel docs,
without providing a example about the desired format.

This patch provides a positive example first in the guide so that it's
harder to miss, then leaves the existing less desirable approach below
for contributors to follow if they have some stronger justification for
why to use that approach.

Signed-off-by: Joe Stringer <joe@isovalent.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20230424171850.3612317-1-joe@isovalent.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>