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>
Change-Id: I492833975e28e9888e412711e80670ca0901010d