Fix: Mesh Filter undo panel not undoing previous change

The `exec` callback was missing a call to `undo::push_end`, meaning that
using the undo panel would not undo the prior step, causing an
accumulative effect.

Pull Request: https://projects.blender.org/blender/blender/pulls/131466

source/blender/editors/sculpt_paint/sculpt_filter_mesh.cc

@@ -2494,6 +2494,7 @@ static int sculpt_mesh_filter_exec(bContext *C, wmOperator *op)
     }
 
     sculpt_mesh_filter_end(C);
+    undo::push_end(*CTX_data_active_object(C));
 
     return OPERATOR_FINISHED;
   }