doc: doxygen: move notify/onoff to os_services

Those are no kernel permitives and belong under os services.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

Author: nashif

include/zephyr/sys/notify.h

@@ -73,7 +73,7 @@ struct sys_notify;
 
 /**
  * @defgroup sys_notify_apis Asynchronous Notification APIs
- * @ingroup kernel_apis
+ * @ingroup os_services
  * @{
  */
 

include/zephyr/sys/onoff.h

@@ -18,7 +18,7 @@ extern "C" {
 
 /**
  * @defgroup resource_mgmt_onoff_apis On-Off Service APIs
- * @ingroup kernel_apis
+ * @ingroup os_services
  * @{
  */