Fix G28 resetting DUAL_NOZZLE_DUPLICATION_MODE (#11605)

There's no reason for G28 to reset DUAL_NOZZLE_DUPLICATION_MODE, because it only affects the E stepper, unlike DUAL_X_CARRIAGE which affects the X steppers as well.

Marlin/src/gcode/calibrate/G28.cpp

     tool_change(0, 0, true);
   #endif
 
-  #if ENABLED(DUAL_X_CARRIAGE) || ENABLED(DUAL_NOZZLE_DUPLICATION_MODE)
+  #if ENABLED(DUAL_X_CARRIAGE)
     extruder_duplication_enabled = false;
   #endif