Commit 487e9861 added a new field to struct Trigger, but failed to
update the documentation to match; backpatch to v13 where that came in.

Reviewed by Richard Guo.

Discussion: https://postgr.es/m/CAPmGK17NY92CyxJ%2BBG7A3JZurmng4jfRfzPiBTtNupGMF0xW1g%40mail.gmail.com