doc: Remove notes about "unencrypted" passwords.

The documentation for the pg_authid system catalog and the
pg_shadow system view indicates that passwords might be stored in
cleartext, but that hasn't been possible for some time.

Oversight in commit eb61136dc7.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/aD2yKkZro4nbl5ol%40nathan
Backpatch-through: 13

doc/src/sgml/catalogs.sgml

@@ -1580,7 +1580,7 @@
        <structfield>rolpassword</structfield> <type>text</type>
       </para>
       <para>
-       Password (possibly encrypted); null if none. The format depends
+       Encrypted password; null if none. The format depends
        on the form of encryption used.
       </para></entry>
      </row>
@@ -1616,11 +1616,6 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
    <replaceable>ServerKey</replaceable> are in Base64 encoded format. This format is
    the same as that specified by <ulink url="https://datatracker.ietf.org/doc/html/rfc5803">RFC 5803</ulink>.
   </para>
-
-  <para>
-    A password that does not follow either of those formats is assumed to be
-    unencrypted.
-  </para>
  </sect1>
 
 
@@ -12560,7 +12555,7 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
        <structfield>passwd</structfield> <type>text</type>
       </para>
       <para>
-       Password (possibly encrypted); null if none.  See
+       Encrypted password; null if none.  See
        <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>
        for details of how encrypted passwords are stored.
       </para></entry>