Spelling correction

Spelling correction

Note: we also have a similar spelling error in:
```
Surface_mesh_skeletonization/benchmark/Surface_mesh_skeletonization/mcf_scale_invariance.cpp:104:  output.open("correspondance.cgal");
Surface_mesh_skeletonization/examples/Surface_mesh_skeletonization/MCF_Skeleton_example.cpp:68:  output.open("correspondance-poly.polylines.txt");
Surface_mesh_skeletonization/examples/Surface_mesh_skeletonization/MCF_Skeleton_LCC_example.cpp:66:  output.open("correspondance-lcc.polylines.txt");
Surface_mesh_skeletonization/examples/Surface_mesh_skeletonization/MCF_Skeleton_om_example.cpp:75:  output.open("correspondance-sm.polylines.txt");
Surface_mesh_skeletonization/examples/Surface_mesh_skeletonization/MCF_Skeleton_sm_example.cpp:67:  output.open("correspondance-sm.polylines.txt");
Surface_mesh_skeletonization/examples/Surface_mesh_skeletonization/simple_mcfskel_example.cpp:72:  output.open("correspondance-poly.polylines.txt");
Surface_mesh_skeletonization/examples/Surface_mesh_skeletonization/simple_mcfskel_LCC_example.cpp:72:  output.open("correspondance-lcc.polylines.txt");
Surface_mesh_skeletonization/examples/Surface_mesh_skeletonization/simple_mcfskel_sm_example.cpp:51:  output.open("correspondance-sm.polylines.txt");
```
but as this in filenames I didn't change it.

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Corefinement/Face_graph_output_builder.h

@@ -1852,7 +1852,7 @@ class Face_graph_output_builder
             if (coplanar_patches_of_tm1.test(patch_id))
             {
               // Two "identical" coplanar patches that are entire connected components
-              //we have the correspondance between cpln patches thanks to faces in tm1_coplanar_faces and tm2_coplanar_faces
+              // we have the correspondence between cpln patches thanks to faces in tm1_coplanar_faces and tm2_coplanar_faces
               CGAL_assertion(tm1_coplanar_faces.size()==tm2_coplanar_faces.size());
               if (coplanar_tm1_to_coplanar_tm2.empty()) // fill container only once
               {