doc: update section about passwords when cloning standbys

Reference new password management section and remove duplicate
info.

doc/cloning-standbys.xml

@@ -458,10 +458,8 @@ description = "Main cluster"
 
     <para>
      The recommended way to do this is to store the password in the <literal>postgres</literal> system
-     user's <filename>~/.pgpass</filename> file. It's also possible to store the password in the
-     environment variable <varname>PGPASSWORD</varname>, however this is not recommended for
-     security reasons. For more details see the
-     <ulink url="https://www.postgresql.org/docs/current/libpq-pgpass.html">PostgreSQL password file documentation</ulink>.
+     user's <filename>~/.pgpass</filename> file.  For more information on using the password file, see
+     the documentation section <xref linkend="configuration-password-file"/>.
     </para>
 
     <note>
@@ -483,19 +481,6 @@ description = "Main cluster"
      will need to be set during any action which causes <filename>recovery.conf</filename> to be
      rewritten, e.g. <xref linkend="repmgr-standby-follow"/>.
     </para>
-    <para>
-     It is of course also possible to include the password value in the <varname>conninfo</varname>
-     string for each node, but this is obviously a security risk and should be avoided.
-    </para>
-    <para>
-      From PostgreSQL 9.6, <application>libpq</application> supports the <varname>passfile</varname>
-      parameter in connection strings, which can be used to specify a password file other than
-      the default <filename>~/.pgpass</filename>.
-    </para>
-    <para>
-      To have &repmgr; write a custom password file in <varname>primary_conninfo</varname>,
-      specify its location in <varname>passfile</varname> in <filename>repmgr.conf</filename>.
-    </para>
    </sect2>
 
    <sect2 id="cloning-advanced-replication-user" xreflabel="Separate replication user">