refactor: remove `stdnoreturn.h` includes

The `noreturn` macro and `_Noreturn` keywords are deprecated in C23. The
reccommended way to indicate noreturn is now `[[noreturn]]`, which uses
the new C23 attribute syntax.

Change-Id: Ib923fce8bbe97597aa5ed27bb0962a107191022b
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
diff --git a/test/hftest/common.c b/test/hftest/common.c
index be4c44c..84ad7e4 100644
--- a/test/hftest/common.c
+++ b/test/hftest/common.c
@@ -104,7 +104,7 @@
 /**
  * Logs a failure message and shut down.
  */
-noreturn void abort(void)
+[[noreturn]] void abort(void)
 {
 	HFTEST_LOG("FAIL");
 	arch_power_off();