Don't document ::CGAL::NTS namespace anymore - it's history.

Developers_manual/doc_tex/Developers_manual/namespaces.tex

@@ -90,9 +90,7 @@ According to the resolutions of the following issues in the forthcoming
 {\tt
 Unless otherwise specified, no global or non-member function in the standard library 
 shall use a function from another namespace which is found through argument-dependent
-name lookup
-}, the namespace \ccc{CGAL::NTS} does not need to be used anymore 
-(currently \ccc{CGAL_NTS} macro boils down to \ccc{CGAL::}).
+name lookup.}
 
 \section{Requirements and recommendations}