R1:be0bb68f6536

Remove Facebook OAuth dependency on "security_settings" property

Summary: Ref T13615. This property was removed from the Facebook API at some point, perhaps November 2020. Stop relying no it.

Test Plan: Created a local Facebook OAuth app, registered a new account locally.

Maniphest Tasks: T13615

Differential Revision: https://secure.phabricator.com/D21571