Fix order of steps in DISCARD ALL documentation

The docs have always been slightly inaccurate, but got particularly so
in a874fe7b, which made DISCARD ALL occur before everything else;
reorder.

Author: Jan Chochol
Discussion: https://postgr.es/m/CAEASf_3TzBbnXm64HpnD5zCZEh8An9jN8ubMR=De-vOXHMHGeA@mail.gmail.com

doc/src/sgml/ref/discard.sgml

@@ -84,15 +84,15 @@ DISCARD { ALL | PLANS | SEQUENCES | TEMPORARY | TEMP }
       Currently, this has the same effect as executing the following sequence
       of statements:
 <programlisting>
+CLOSE ALL;
 SET SESSION AUTHORIZATION DEFAULT;
 RESET ALL;
 DEALLOCATE ALL;
-CLOSE ALL;
 UNLISTEN *;
 SELECT pg_advisory_unlock_all();
 DISCARD PLANS;
-DISCARD SEQUENCES;
 DISCARD TEMP;
+DISCARD SEQUENCES;
 </programlisting></para>
     </listitem>
    </varlistentry>