Revert "Allowe system_app to access UEvent"

This reverts commit 615c724feef6d10eafc5730210f520353be111f6.

This doesn't compile, and actually I intented to target platform_app,
which already have this permission.
diff --git a/sepolicy/hardware_overlay.te b/sepolicy/hardware_overlay.te
index 2da458c..d3bb487 100644
--- a/sepolicy/hardware_overlay.te
+++ b/sepolicy/hardware_overlay.te
@@ -1,2 +1 @@
 allow priv_app overlay_service:service_manager find;
-allow system_app self:netlink_kobject_uevent_socket create_socket_perms_no_ioctl;