doc: Remove PostgreSQL version number from xml2 deprecation notice

It is obviously no longer true.

doc/src/sgml/xml2.sgml

@@ -21,11 +21,11 @@
    That functionality covers XML syntax checking and XPath queries,
    which is what this module does, and more, but the API is
    not at all compatible.  It is planned that this module will be
-   removed in PostgreSQL 8.4 in favor of the newer standard API, so
+   removed in a future version of PostgreSQL in favor of the newer standard API, so
    you are encouraged to try converting your applications.  If you
    find that some of the functionality of this module is not
    available in an adequate form with the newer API, please explain
-   your issue to pgsql-hackers@postgresql.org so that the deficiency
+   your issue to <email>pgsql-hackers@postgresql.org so</email> that the deficiency
    can be addressed.
   </para>
  </sect2>