pgsql: Use OFFSET 0 instead of ORDER BY to stop subquery pullup

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

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/5dc582da6b9a281321e687ae2b52f96b929d8d0e

Modified Files
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src/test/regress/expected/memoize.out | 4 ++--
src/test/regress/sql/memoize.sql | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)