Removing stats service registration in system server

Introduced in ag/2837473, this stats service is not actually up and
running fully. It is creating boot time selinux denials due to lack of
permissions for system server to start the service. Since it cannot run
due to system server being unable to register it with servicemanager, the
registration code is being removed for now to clean up boot denials.

Removing this boot denial will allow boot-time presubmit tests for SELinux to be
put into place. Service definition and sepolicy for this feature can be
added when the feature is approved in the future.

Bug: 67468181
Test: servicemanager does not generate denials on boot
Change-Id: Id6a29cc6abb8ebf5a3f41da4311a555f41dd80b3