docs: Retire old resources from kernel-docs.rst

Remove outdated or obsolete resources from process/kernel-docs.rst, with
the exception of foundational material. Update information regarding
LWN.net. See Link below for further context.

Link: https://lore.kernel.org/lkml/093907af-2e4e-d232-1eb0-7331ff2b9320@amd.com/Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
Link: https://lore.kernel.org/r/20221124170242.1892751-3-carlos.bilbao@amd.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>