message: Update way of checking for registration disabled
  Spec says 403 + M_FORBIDDEN
diff: @@ -223,7 +223,7 @@ export default class Registration extends React.Component<IProps, IState> {
  this.setState({
  flows: e.data.flows,
  });
  - } else if (e.httpStatus === 403 && e.errcode === "M_UNKNOWN") {
  + } else if (e.httpStatus === 403 || e.errcode === "M_FORBIDDEN") {
  // At this point registration is pretty much disabled, but before we do that let's
  // quickly check to see if the server supports SSO instead. If it does, we'll send
  // the user off to the login page to figure their account out.
  