ANDROID: gki_defconfig: Disable CONFIG_RT_GROUP_SCHED

Disable CONFIG_RT_GROUP_SCHED to control RT cpu allowance globally.

ABI update report:

 ABI DIFFERENCES HAVE BEEN DETECTED! (RC=8)
========================================================
Leaf changes summary: 2 artifacts changed
Changed leaf types summary: 2 leaf types changed
Removed/Changed/Added functions summary: 0 Removed, 0 Changed, 0 Added function
Removed/Changed/Added variables summary: 0 Removed, 0 Changed, 0 Added variable

'struct sched_rt_entity at sched.h:481:1' changed:
  type size changed from 576 to 384 (in bits)
  3 data member deletions:
    'sched_rt_entity* sched_rt_entity::parent', at offset 384 (in bits) at sched.h:491:1

    'rt_rq* sched_rt_entity::rt_rq', at offset 448 (in bits) at sched.h:493:1

    'rt_rq* sched_rt_entity::my_q', at offset 512 (in bits) at sched.h:495:1

  1033 impacted interfaces
========================================================

Bug: 149954332
Change-Id: I9487bd113502e52f19637e43109433cb13e97a23
Signed-off-by: Suren Baghdasaryan <surenb@google.com>