Change keyboard level include guards to pragma once (#14248)

* Change keyboard level include guards to `pragma once`

And clean up a lot of layout macros

* Oops

* Remove dangling endif

keyboards/hhkb/rn42/rn42_task.h

@@ -1,5 +1,4 @@
-#ifndef RN42_TASK_H
-#define RN42_TASK_H
+#pragma once
 
 #include <stdbool.h>
 #include "rn42.h"
@@ -10,5 +9,3 @@ bool rn42_nkro_last;
 
 void rn42_task_init(void);
 void rn42_task(void);
-
-#endif