packagegroups: Remove obmc-mgr-system

The system manager (obmc-mgr-system) which provided GPIO
functionality is being deprecated and it's not in use anymore:
* GPIOs have moved out of D-Bus (see openbmc/openbmc#3332).
* Tools depending on its GPIO functions have been updated to
call local functions instead.
* The systemd service files have been updated to not depend
on system manager.

Change-Id: Ide5492192d4cb5bb373e75831c0f8eafa283f8e2
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
2 files changed