pgsql: Minor tweak to make rowtypes regression test run faster.

Log Message:
-----------
Minor tweak to make rowtypes regression test run faster.  We don't
currently have any better strategy for this query than re-running the
sub-select over and over; it seems unlikely that doing so 10000 times
is a more useful test than doing it a few dozen times.

Modified Files:
--------------
    pgsql/src/test/regress/sql:
        rowtypes.sql (r1.5 -> r1.6)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/rowtypes.sql.diff?r1=1.5&r2=1.6)
    pgsql/src/test/regress/expected:
        rowtypes.out (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/rowtypes.out.diff?r1=1.8&r2=1.9)