use pod link instead of url for 5to6-nutshell

Author: jsoref

doc/Language/5to6-perlsyn.pod

@@ -44,8 +44,7 @@ No more. That would now have to be C<%seen{$_}++>.
 If it makes you feel better, you can use backslashes to "unspace" whitespace,
 so you can use whitespace where it would otherwise be forbidden.
 
-You can find the details on this at
-L<http://doc.perl6.org/language/5to6-nutshell#Whitespace>.
+See L<Whitespace|/language/5to6-nutshell#Whitespace> for details.
 
 =head2 Declarations