[Keyboard] Update MNK88 RGB Underglow LED Number (#17833)

Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Ryan <fauxpark@gmail.com>

keyboards/kopibeng/mnk88/config.h

@@ -50,7 +50,7 @@
 
 #define RGB_DI_PIN A10
 #ifdef RGB_DI_PIN
-    #define RGBLED_NUM 19
+    #define RGBLED_NUM 20
     #define RGBLIGHT_HUE_STEP 8
     #define RGBLIGHT_SAT_STEP 8
     #define RGBLIGHT_VAL_STEP 8