init.rc: remove system cgroup migraion

We never use CONFIG_RT_GROUP_SCHED in GKI kernel, but that could be set
on legacy devices. Remove system cgroup migration and also RT settings
as we should not have any task under those groups.

Bug: 191925901
Test: Build
Signed-off-by: Wei Wang <wvw@google.com>
Merged-In: I492833975e28e9888e412711e80670ca0901010d
Change-Id: I492833975e28e9888e412711e80670ca0901010d
(cherry picked from commit b4e79853)