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

quantum/process_keycode/process_steno.h

@@ -13,8 +13,8 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-#ifndef PROCESS_STENO_H
-#define PROCESS_STENO_H
+
+#pragma once
 
 #include "quantum.h"
 
@@ -25,5 +25,3 @@ void     steno_init(void);
 void     steno_set_mode(steno_mode_t mode);
 uint8_t *steno_get_state(void);
 uint8_t *steno_get_chord(void);
-
-#endif