Docs/admin-guide/mm/damon/usage: update for tried regions update time interval

The documentation says DAMOS tried regions update feature of DAMON sysfs
interface is doing the update for one aggregation interval after the
request is made.  Since the introduction of the per-scheme apply interval,
that behavior makes no much sense.  Hence the implementation has changed
to update the regions for each scheme for only its apply interval. 
Further update the document to reflect the real behavior.

Link: https://lkml.kernel.org/r/20231012192256.33556-4-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>