Fix: Grease Pencil: Sculpt Smooth Tool Bezier Handles

This makes so that bezier handles will be smoothed by the `Smooth Tool`.

Note: A `BLI_assert` is removed, the logic used was wrong.

Pull Request: https://projects.blender.org/blender/blender/pulls/141912

source/blender/blenkernel/intern/curves_utils.cc

@@ -199,7 +199,6 @@ void write_all_positions(bke::CurvesGeometry &curves,
   {
     return;
   }
-  BLI_assert(curves_selection.size() * 3 == all_positions.size());
 
   const OffsetIndices points_by_curve = curves.points_by_curve();
   MutableSpan<float3> positions = curves.positions_for_write();

source/blender/editors/sculpt_paint/grease_pencil_sculpt_smooth.cc

@@ -147,16 +147,9 @@ void SmoothOperation::on_stroke_extended(const bContext &C, const InputSample &e
 
         bool changed = false;
         if (sculpt_mode_flag & GP_SCULPT_FLAGMODE_APPLY_POSITION) {
-          MutableSpan<float3> positions = curves.positions_for_write();
-          geometry::smooth_curve_attribute(curves.curves_range(),
-                                           points_by_curve,
-                                           selection_varray,
-                                           cyclic,
-                                           iterations,
-                                           influences,
-                                           false,
-                                           false,
-                                           positions);
+          geometry::smooth_curve_positions(
+              curves, curves.curves_range(), iterations, influences, false, false);
+
           params.drawing.tag_positions_changed();
           changed = true;
         }