PG 10 release notes: change trigger transition tables

Add attribution of trigger transition tables for Thomas Munro.

Reported-by: Thomas Munro

Discussion: https://postgr.es/m/CAEepm=2bDFgr4ut+1-QjKQY4MA=5ek8Ap3nyB19y2tpTL6xxtA@mail.gmail.com

Backpatch-through: 10