Update gds-sso

When using gds-sso mocking in development, was getting a lot of
signin permission bits created.

```
irb(main):001:0> User.first.permissions
    User Load (0.5ms)  SELECT `users`.* FROM `users` LIMIT 1
=> [["signin"], ["signin"], ["signin"], ["signin"], ["signin"]]
```

See https://github.com/alphagov/gds-sso/commit/10b59e8155bb6f09899f6b38e5abec39c575e0cf