pgsql: Forgot to back-patch earlier change to documentation for

Log Message:
-----------
Forgot to back-patch earlier change to documentation for aggregate
ORDER BY clauses.

Tags:
----
REL9_0_STABLE

Modified Files:
--------------
pgsql/doc/src/sgml:
syntax.sgml (r1.147 -> r1.147.2.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/syntax.sgml?r1=1.147&r2=1.147.2.1)