Update pins_BIQU_SKR_V1.1.h (#12758)

Marlin/src/pins/pins_BIQU_SKR_V1.1.h

 // Heaters / Fans
 //
 #define HEATER_0_PIN       P2_07
-#define HEATER_1_PIN       P2_04
+#if HOTENDS == 1
+  #define FAN1_PIN         P2_04
+#else
+  #define HEATER_1_PIN     P2_04
+#endif 
 #define FAN_PIN            P2_03
 #define HEATER_BED_PIN     P2_05