🔧 No Switching Nozzle with MMU2

Marlin/src/inc/SanityCheck.h

     #error "SWITCHING_NOZZLE and DUAL_X_CARRIAGE are incompatible."
   #elif ENABLED(SINGLENOZZLE)
     #error "SWITCHING_NOZZLE and SINGLENOZZLE are incompatible."
+  #elif HAS_PRUSA_MMU2
+    #error "SWITCHING_NOZZLE and PRUSA_MMU2(S) are incompatible."
   #elif EXTRUDERS != 2
     #error "SWITCHING_NOZZLE requires exactly 2 EXTRUDERS."
   #elif NUM_SERVOS < 1