sched/headers: Remove <linux/magic.h> from <linux/sched/task_stack.h>

It's not used by any of the scheduler methods, but <linux/sched/task_stack.h>
needs it to pick up STACK_END_MAGIC.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

@@ -22,7 +22,6 @@
 #include <linux/task_io_accounting.h>
 #include <linux/latencytop.h>
 #include <linux/topology.h>
-#include <linux/magic.h>
 
 #include <asm/current.h>
 

kernel/cgroup/cgroup-v1.c

@@ -7,6 +7,7 @@
 #include <linux/mm.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/task.h>
+#include <linux/magic.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/delayacct.h>