Change include guards in quantum/ to pragma once (#11239)

quantum/process_keycode/process_terminal_nop.h

@@ -14,12 +14,9 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef PROCESS_TERMINAL_H
-#define PROCESS_TERMINAL_H
+#pragma once
 
 #include "quantum.h"
 
 #define TERM_ON KC_NO
 #define TERM_OFF KC_NO
-
-#endif