"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 86f57594; back-patch to v11 where that
commit came in.

Reviewed by Tom Lane.

Discussion: https://postgr.es/m/CAPmGK17gk4vXLzz2iG%2BG4LWRWCoVyam70nZ3OuGm1hMJwDrhcg%40mail.gmail.com