Google oauth is done via the /auth route, not config settings.

Summary:
http://phabricator.khanacademy.org/config/issue/ told me:
    Unknown Configuration Option "google.application-id"
    Unknown Configuration Option "google.application-secret"
    Unknown Configuration Option "google.auth-enabled"
    Unknown Configuration Option "google.auth-permanent"
    Unknown Configuration Option "google.registration-enabled"

Asking on IRC, I found out these config options have gone away -- the
data is stored in a database now, I guess?  Anyway, the phabricator
update script must have automatically populated the database for us
based on our config settings, because google oauth still works.  We
can just get rid of these now-obsolete settings.

Test Plan: Fingers crossed.

Reviewers: chris

Reviewed By: chris

Differential Revision: http://phabricator.khanacademy.org/D2773