Clarify 'cert' authentication documention.

doc/src/sgml/client-auth.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/client-auth.sgml,v 1.118 2009/01/09 10:13:18 mha Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/client-auth.sgml,v 1.119 2009/03/22 21:55:07 momjian Exp $ -->
 
 <chapter id="client-authentication">
  <title>Client Authentication</title>
@@ -1245,9 +1245,9 @@ ldapserver=ldap.example.net prefix="cn=" suffix="dc=example, dc=net"
     When using this authentication method, the server will require that
     the client provide a certificate. No password prompt will be sent
     to the client. The <literal>cn</literal> attribute of the certificate
-    will be matched with the username the user is trying to log in as,
-    and if they match the login will be allowed. Username mapping can be
-    used if the usernames don't match.
+    will be matched with the login username, and if they match the
+    login will be allowed. Username mapping can be used if the usernames
+    don't match.
    </para>
   </sect2>