Update tests after OIDC changes

See https://github.com/ral-facilities/ldap-jwt-auth/pull/272#issuecomment-3301576445 and https://github.com/ral-facilities/ldap-jwt-auth/pull/271#issuecomment-3352522006. Once https://github.com/ral-facilities/ldap-jwt-auth/pull/271 is merged it should be possible to add/remove/update the tests as required.