Merge pull request #3440 from floyd871/patch-1

Wrong Pin Assignment Megatronics 3

Marlin/pins_MEGATRONICS_3.h

 #define SERVO0_PIN         46 //AUX3-6
 #define SERVO1_PIN         47 //AUX3-5
 #define SERVO2_PIN         48 //AUX3-4
-#define SERVO2_PIN         49 //AUX3-3
+#define SERVO3_PIN         49 //AUX3-3
 
 #define X_STEP_PIN         58
 #define X_DIR_PIN          57