Fix #105681: Sculpt trim generates smooth shaded faces

Caused by 5876573e14. We need to use the old default here
explicitly.

source/blender/editors/sculpt_paint/paint_mask.cc

@@ -1300,6 +1300,8 @@ static void sculpt_gesture_trim_geometry_generate(SculptGestureContext *sgcontex
     loop_index += 3;
   }
 
+  BKE_mesh_smooth_flag_set(trim_operation->mesh, false);
+
   BKE_mesh_calc_edges(trim_operation->mesh, false, false);
   sculpt_gesture_trim_normals_update(sgcontext);
 }