BUG #17034: Creating aggregate function based on array_append now results in "function does not exist" error

The following bug has been logged on the website:

Bug reference:      17034
Logged by:          Adam Rauch
Email address:      adam@labkey.com
PostgreSQL version: 14beta1
Operating system:   Windows 10
Description:

The DDL below has executed correctly on every PostgreSQL version through
13.x. In 14 beta 1, it produces: "ERROR:  function array_append(anyarray,
anyelement) does not exist  SQL state: 42883"

CREATE AGGREGATE core.array_accum (anyelement)
(
  sfunc = array_append,
  stype = anyarray,
  initcond = '{}'
);

We long ago stopped using this aggregate function (switched to built-in
functions array_agg and string_agg), so we can simply remove this DDL (i.e.,
we don't care if it's fixed or not). But other systems may be affected by
this change. If nothing else, a mention in the release notes would be
helpful.