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/handwired/nicekey/nicekey.h

@@ -1,12 +1,9 @@
-#ifndef NICEKEY_H
-#define NICEKEY_H
+#pragma once
 
 #include "quantum.h"
 
 #define LAYOUT( \
     k00 \
-  ) { \
-    { k00 }  \
+) { \
+    { k00 } \
 }
-
-#endif