Fix trailing whitespace

Marlin/src/module/planner.cpp

       // In worst case, only one extruder running, no change is needed.
       // In best case, all extruders run the same amount, we can divide by MIXING_STEPPERS
       float delta_mm_i = 0;
-      if (i == E_AXIS && mixer.get_current_v_tool() == MIXER_AUTORETRACT_TOOL) 
+      if (i == E_AXIS && mixer.get_current_v_tool() == MIXER_AUTORETRACT_TOOL)
         delta_mm_i = delta_mm[i] / MIXING_STEPPERS;
       else
         delta_mm_i = delta_mm[i];