pgsql: Fix test case from 40c242830

Fix test case from 40c242830

I mistakenly included the "Replaces" lines describing the origin of
Result nodes in groupingsets.out, which actually come from a feature
not available in v18. Mea culpa.

Per buildfarm.

Discussion: /messages/by-id/CAMbWs4_VxjdM-nBvt8YE=84rE4OLBES27Wz1P0=9Z6KgwPqzEA@mail.gmail.com

Branch
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REL_18_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/ee49f2cf447ab3191164aec82410dc52f7960c6f

Modified Files
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src/test/regress/expected/groupingsets.out | 21 +++++++++------------
1 file changed, 9 insertions(+), 12 deletions(-)