Corrected the point to the BLFS installation page for DocBook-XML DTD in the INSTALL file.

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@3723 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

INSTALL

@@ -18,7 +18,7 @@ If all you want to do is convert XML to HTML perform the following:
   - http://www.linuxfromscratch.org/blfs/view/cvs/general/libxslt.html
 
 * DocBook DTD 
-  - http://www.linuxfromscratch.org/blfs/view/cvs/pst/sgml-dtd.html
+  - http://www.linuxfromscratch.org/blfs/view/cvs/pst/DocBook.html
 
 * DocBook XSL Stylesheets 
   - http://www.linuxfromscratch.org/blfs/view/cvs/pst/docbook-xsl.html