Update obsolete portgroup docs about replaced_by

replaced_by can now be specified either before or after including the
portgroup.

See: https://trac.macports.org/ticket/56023

guide/xml/portfiledev.xml

@@ -1081,9 +1081,10 @@ To report a bug, see &lt;https://guide.macports.org/#project.tickets&gt;</screen
 # -*- coding: utf-8; mode: tcl; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- vim:fenc=utf-8:ft=tcl:et:sw=4:ts=4:sts=4
 
 PortSystem          1.0
-replaced_by         skrooge
 PortGroup           obsolete 1.0
+
 name                skrooge-devel
+replaced_by         skrooge
 svn.revision        1215845
 version             0.8.0-${svn.revision}
 revision            2
@@ -1097,8 +1098,8 @@ categories          kde finance
           <filename>${prefix}/var/macports/sources/rsync.macports.org/macports/release/tarballs/ports/_resources/port1.0/group/obsolete-1.0.tcl</filename>.</para>
 
         <note>
-          <para>It is important to specify <varname>replaced_by</varname> BEFORE the
-            <varname>PortGroup</varname> line!</para>
+          <para><varname>replaced_by</varname> can be specified before or after the
+            <varname>PortGroup</varname> line.</para>
         </note>
 
       </section>