Update DAMON ABI document for the newly added DAMO filter type, 'young
page'.

Link: https://lkml.kernel.org/r/20240426195247.100306-8-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Honggyu Kim <honggyu.kim@sk.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>