pgsql: Fix misleading error message about inconsistent moving-aggregate

Fix misleading error message about inconsistent moving-aggregate types.

We reported the wrong types when complaining that an aggregate's
moving-aggregate implementation is inconsistent with its regular
implementation.

This was wrong since the feature was introduced, so back-patch
to all supported branches.

Jeff Janes

Discussion: https://postgr.es/m/CAMkU=1x808LH=LPhZp9mNSP0Xd1xDqEd+XeGcvEe48dfE6xV=A@mail.gmail.com

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2939f613fa91f12b43d51eb8c4e595d5164e5254

Modified Files
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src/backend/catalog/pg_aggregate.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)