Fix #115548: Missed sort after multithreaded algorithm

To make sure result is deterministic, sorting is used.
This was missed in one of last speedup.

Pull Request: https://projects.blender.org/blender/blender/pulls/115568

source/blender/blenkernel/intern/mesh_mapping.cc

@@ -403,6 +403,7 @@ GroupedSpan<int> build_vert_to_edge_map(const Span<int2> edges,
       }
     }
   });
+  sort_small_groups(offsets, 1024, r_indices);
   return {offsets, r_indices};
 }