Use OFFSET 0 instead of ORDER BY to stop subquery pullup
b762fed64 recently changed this test to prevent subquery pullup to allow
us to test Memoize with lateral_vars. As pointed out by Tom Lane, OFFSET
0 is our standard way of preventing subquery pullups, so do it that way
instead.
Discussion: https://postgr.es/m/
2144818.
1674517061@sss.pgh.pa.us
Backpatch-through: 14, same as
b762fed64