enable prod standalone sign in page (#13540)
enable prod standalone sign in page (#13540)

* custom login is a valid auth type

type=custom is the auth type used for SSOe auto logins, no need to
capture a sentry error when this happens

* enabling the standalone sign in page in prod

* must have been a bad merge, case custom is already in the switch
department-of-veterans-affairs/vets-website,department-of-veterans-affairs/vets-website