Fix the rendering of an xref to man pages on the shadow page

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11484 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter06/shadow.xml

@@ -51,8 +51,8 @@
 
     <para>Disable the installation of the <command>groups</command> program
     and its man pages, as Coreutils provides a better version. Also 
-    Prevent the installation of manual pages that were already installed by the
-    <xref linkend="man-pages"/> package:</para>
+    Prevent the installation of manual pages that were already installed in
+    <xref linkend="ch-system-man-pages"/>:</para>
 
 <screen><userinput remap="pre">sed -i 's/groups$(EXEEXT) //' src/Makefile.in
 find man -name Makefile.in -exec sed -i 's/groups\.1 / /'   {} \;