Correct fan pins for MKS Robin Nano v3 (#21238)

Marlin/src/pins/stm32f4/pins_MKS_ROBIN_NANO_V3.h

@@ -165,8 +165,8 @@
 #define HEATER_1_PIN                        PB0   // HEATER2
 #define HEATER_BED_PIN                      PA0   // HOT BED
 
-#define FAN_PIN                             PB1   // FAN
-#define FAN1_PIN                            PC14  // FAN1
+#define FAN_PIN                             PC14  // FAN
+#define FAN1_PIN                            PB1   // FAN1
 
 //
 // Thermocouples