pgsql: Correct error message for row-level triggers with transition tab

Correct error message for row-level triggers with transition tables on partitioned tables.

"Triggers on partitioned tables cannot have transition tables." is
incorrect as we allow statement-level triggers on partitioned tables to
have transition tables.

This has been wrong since commit 86f575948; back-patch to v11 where that
commit came in.

Reviewed by Tom Lane.

Discussion: /messages/by-id/CAPmGK17gk4vXLzz2iG+G4LWRWCoVyam70nZ3OuGm1hMJwDrhcg@mail.gmail.com

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/6f47756d6fa87c1bb155c4a04752d3837620da0c

Modified Files
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src/backend/commands/trigger.c | 2 +-
src/test/regress/expected/triggers.out | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)