doc, mm: sync up oom_score_adj documentation

There are at least two notes in the oom section.  The 3% discount for root
processes is gone since d46078b2 ("mm, oom: remove 3% bonus for
CAP_SYS_ADMIN processes").

Likewise children of the selected oom victim are not sacrificed since
bbbe4802 ("mm, oom: remove 'prefer children over parent' heuristic")

Drop both of them.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Link: http://lkml.kernel.org/r/20200709062603.18480-1-mhocko@kernel.orgSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/filesystems/proc.rst

@@ -1633,9 +1633,6 @@ may allocate from based on an estimation of its current memory and swap use.
 For example, if a task is using all allowed memory, its badness score will be
 1000.  If it is using half of its allowed memory, its score will be 500.
 
-There is an additional factor included in the badness score: the current memory
-and swap usage is discounted by 3% for root processes.
-
 The amount of "allowed" memory depends on the context in which the oom killer
 was called.  If it is due to the memory assigned to the allocating task's cpuset
 being exhausted, the allowed memory represents the set of mems assigned to that
@@ -1671,11 +1668,6 @@ The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
 requires CAP_SYS_RESOURCE.
 
-Caveat: when a parent task is selected, the oom killer will sacrifice any first
-generation children with separate address spaces instead, if possible.  This
-avoids servers and important system daemons from being killed and loses the
-minimal amount of work.
-
 
 3.2 /proc/<pid>/oom_score - Display current oom-killer score
 -------------------------------------------------------------