tools:cgroup:memcg_shrinker remove redundant import

Remove redundant import of the sys module.

Also use the sort function instead of sorted.  It sorts the direct array
without create the new one in memory.

Link: https://lkml.kernel.org/r/20230108105023.4289-1-apantykhin@gmail.com


Signed-off-by: Alexander Pantyukhin <apantykhin@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>