Fix link directive, resolves mistake from 6fb710b.

Inverted the L<> directive text and link.

Author: fluca1978

doc/Language/5to6-perlvar.pod6

@@ -55,7 +55,7 @@ C<.shift> does not).
 =item $"
 
 Currently, there is no equivalent of the List Separator variable in Perl 6.
-Design document L<https://design.perl6.org/S28.html|S28> says there isn't one,
+Design document L<S28|https://design.perl6.org/S28.html> says there isn't one,
 so you probably don't want to hold your breath.
 
 =item $PROCESS_ID