pgsql: Remove one memoize test case added by commit 069d0ff02.

Remove one memoize test case added by commit 069d0ff02.

This test case turns out to depend on the assumption that a non-Var
subquery output that's underneath an outer join will always get
wrapped in a PlaceHolderVar. But that behavior causes performance
regressions in some cases compared to what happened before v16.
The next commit will avoid inserting a PHV in the same cases where
pre-v16 did, and that causes get_memoized_path to not detect that
a memoize plan could be used.

Commit this separately, in hopes that we can restore the test after
making get_memoized_path smarter. (It's failing to find memoize
plans in adjacent cases where no PHV was ever inserted, so there
is definitely room for improvement there.)

Discussion: https://postgr.es/m/CAG1ps1xvnTZceKK24OUfMKLPvDP2vjT-d+F2AOCWbw_v3KeEgg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3409b4db631f5471696127494e57193350b87b41

Modified Files
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src/test/regress/expected/memoize.out | 30 ------------------------------
src/test/regress/sql/memoize.sql | 11 -----------
2 files changed, 41 deletions(-)