kernel: Remove z_sched_abort() prototype

The routine z_sched_abort() no longer exists.

Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>

kernel/include/ksched.h

diff --git a/kernel/include/ksched.h b/kernel/include/ksched.h
index 7d5a880..e82d1d1 100644
--- a/kernel/include/ksched.h
+++ b/kernel/include/ksched.h
@@ -57,7 +57,6 @@
 
 void z_time_slice(void);
 void z_reset_time_slice(struct k_thread *curr);
-void z_sched_abort(struct k_thread *thread);
 void z_sched_ipi(void);
 void z_sched_start(struct k_thread *thread);
 void z_ready_thread(struct k_thread *thread);