pg_upgrade (12->14) fails on aggregate

Hi Team,

we experienced pg_upgrade failing when attempted to upgrade from 12.10 to 14.2 
(on AWS RDS)

We had this aggregate:

CREATE AGGREGATE public.array_accum(anyelement) ( SFUNC = array_append, STYPE 
= anyarray, INITCOND = '{}');

Syntax in version 14 is changed (we didn't try to run version 13)

We solved it (in our case) dropping the aggregate before upgrade and re-create 
in using new syntax in V14:

CREATE AGGREGATE public.array_accum(anycompatible) ( SFUNC = array_append, 
STYPE = anycompatiblearray, INITCOND = '{}');

but pg_upgrade shouldn't fail on this.

I hope it can help to improve pg_upgrade process.

Thanks.

--
Best
Petr