BUG #16123: DST not respected for America/Sao_Paulo in `timestamp` function

The following bug has been logged on the website:

Bug reference:      16123
Logged by:          Thushara Wijeratna
Email address:      thushw@gmail.com
PostgreSQL version: 11.5
Operating system:   MacOS (Mojave)
Description:

maestro_development=# select timestamp with time zone '2019-12-01T02:00:00Z'
at time zone 'America/Sao_Paulo';
      timezone
---------------------
 2019-11-30 23:00:00
(1 row)

From Nov 3, America/Sao_Paulo should be offset only 2 hours from UTC due to
DTS. I would expect the timestamp to be December 1st midnight.

https://www.travelmath.com/time-zone/America/Sao_Paulo