kmsan: drop the declaration of kmsan_save_stack()

This function is not defined anywhere.

Link: https://lkml.kernel.org/r/20250507160012.3311104-3-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Bart van Assche <bvanassche@acm.org>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/kmsan/kmsan.h

@@ -121,7 +121,6 @@ static __always_inline void kmsan_leave_runtime(void)
 	KMSAN_WARN_ON(--ctx->kmsan_in_runtime);
 }
 
-depot_stack_handle_t kmsan_save_stack(void);
 depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags,
 						 unsigned int extra_bits);