Docs/admin-guide/mm/damon/usage: fix wrong quotas diabling condition

After the introduction of DAMOS quotas, DAMOS quotas is not disabled if
both size and time quotas are zero but the quota goal is set.  The new
rule is also applied to DAMON sysfs interface, but the usage doc is not
updated.  Update it.

Link: https://lkml.kernel.org/r/20240217005842.87348-6-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>