[puppet][congress] Retiring puppet-congress

Hello, As you know, Congress project has been retired already[1], so we will retire its puppet module, puppet-congress in openstack puppet project as well. [1] http://lists.openstack.org/pipermail/openstack-discuss/2020-April/014292.htm... Because congress was directly retired instead of getting migrated to x namespace, we'll follow the same way about puppet-congress retirement and won't create x/puppet-congress. Thank you for the contribution made for the project ! Please let us know if you have any concerns about this retirement. Thank you, Takashi Kajinami