keyten/kt60_mu - Add missing header guard (#25011)

keyboards/keyten/kt60_mu/config.h

@@ -1,6 +1,8 @@
 // Copyright 2024 QMK
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#pragma once
+
 #define BACKLIGHT_PWM_DRIVER PWMD2
 #define BACKLIGHT_PWM_CHANNEL 4
 #define BACKLIGHT_PAL_MODE 2