pgsql: Back-patch test modifications that were done as part of b6df0798

Back-patch test modifications that were done as part of b6df0798a5.

This commit fixes the intermittent buildfarm failures in 031_column_list.
I missed to back-patch while committing b6df0798a5 in the HEAD.

Diagnosed-by: Amit Kapila
Author: Vignesh C
Backpatch-through: 15
Discussion: https://postgr.es/m/3307255.1706911634@sss.pgh.pa.us

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/b5abeb751419a49ab61e93e4ba21583fa9a5e09b

Modified Files
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src/test/subscription/t/031_column_list.pl | 43 +++++++++++++++++++-----------
1 file changed, 28 insertions(+), 15 deletions(-)