PMP: Remove documentation of deprecated code (#7812)

## Summary of Changes

cleanup

## Release Management

* Affected package(s): PMP
* Issue(s) solved (if any): fix #7692

Polygon_mesh_processing/include/CGAL/polygon_mesh_processing.h

@@ -49,21 +49,3 @@
 #include <CGAL/Polygon_mesh_processing/smooth_mesh.h>
 #include <CGAL/Polygon_mesh_processing/smooth_shape.h>
 #include <CGAL/Polygon_mesh_processing/manifoldness.h>
-
-// the named parameter header being not documented the doc is put here for now
-#ifdef DOXYGEN_RUNNING
-namespace CGAL {
-namespace Polygon_mesh_processing {
-namespace parameters {
-
-/*! \ingroup namedparameters
-\deprecated This function is deprecated and `default_values()` should be used instead.
-This function can be used to indicate that all optional named parameters
-to be used are the default ones. This is particularly useful when a function
-requires more than one sequence of named parameters and default values is
-fine only for some of them.
-*/
-unspecified_type all_default();
-
-} } } // end of namespace CGAL::Polygon_mesh_processing::parameters
-#endif