handwired/promethium: fix missing include (#16317)

keyboards/handwired/promethium/promethium.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <stdint.h>
+#include "quantum.h"
 
 void battery_poll(uint8_t level);
 void led_set_kb(uint8_t usb_led);