pgsql: Revert "Temporarily install debugging in partition_prune test"

Revert "Temporarily install debugging in partition_prune test"

1db689715 added debugging output to the partition_prune regression test
to help us figure out why buildfarm member Parula was occasionally
failing.

We've not seen any failures in around 4 weeks and the best guess as to
what the problem was is a compiler bug.  Since there are no recent
failures, there's now no need to keep this debugging code, so revert it.

Discussion: https://postgr.es/m/CAApHDvqyLF881EvDtXT=ossa0i4ioJBtW2c0Wbouzt5d3HDb5Q@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ec1a405adc24bc20523eef83ccc85232ec23eaa9

Modified Files
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src/test/regress/expected/partition_prune.out | 62 ---------------------------
src/test/regress/sql/partition_prune.sql      | 14 ------
2 files changed, 76 deletions(-)