BUG #17210: Postgres Let'sEncrypt root certificate is expired and breaks installation of postgres-client

The following bug has been logged on the website:

Bug reference:      17210
Logged by:          Andres Ehrenpreis
Email address:      andres.ehrenpreis@gmail.com
PostgreSQL version: 11.12
Operating system:   Ubuntu 16.04.7 LTS
Description:

When installing Postgres through Chef like this:

# PostgreSQL database client:
postgresql_client_install "Install PostgreSQL-client v11" do
  version "11"
end

Then server-deployment fails with the error as follows:
[2021-10-01T12:06:52+00:00] ERROR: SSL Validation failure connecting to
host: download.postgresql.org - SSL_connect returned=1 errno=0 state=error:
certificate verify failed (certificate has expired)

Looks like download.postgresql.org cert-chain is broken.