Change include guards in tmk_core/ and drivers/ to pragma once (#11240)

tmk_core/common/sleep_led.h

@@ -1,5 +1,4 @@
-#ifndef SLEEP_LED_H
-#define SLEEP_LED_H
+#pragma once
 
 #ifdef SLEEP_LED_ENABLE
 
@@ -16,5 +15,3 @@ void sleep_led_toggle(void);
 #    define sleep_led_toggle()
 
 #endif
-
-#endif