Update CREATE TRIGGER syntax to use EXECUTE FUNCTION

Prior to Postgres 11, the syntax for creating a trigger was:

CREATE TRIGGER ... EXECUTE PROCEDURE function_name (arguments)

They keyword PROCEDURE was used even though the trigger called a Postgres FUNCTION created with the CREATE FUNCTION command.

Postgres 11 added procedures as a separate concept from functions, with some differences in semantics. As a result, it seems the syntax for creating a trigger was updated to accept either EXECUTE PROCEDURE or EXECUTE FUNCTION, with the latter now being preferred. The official docs say:

In the syntax of CREATE TRIGGER, the keywords FUNCTION and PROCEDURE are equivalent, but the referenced function must in any case be a function, not a procedure. The use of the keyword PROCEDURE here is historical and deprecated.

For reference: https://www.postgresql.org/docs/11/sql-createtrigger.html

In PG 12, it seems the pg_get_triggerdef() function has also been updated to display the trigger definition using the FUNCTION keyword instead of the PROCEDURE keyword, so the app should use the new terminology going forward.