task(crypto_tests): Fix test that will fail when we handle backups co…

…rrectly

This test was checking that a new device which has access to backups
returned an unknown UTD when it was given empty JSON for the event. It
was only passing because we currently have incorrect behaviour when
backups are enabled.

The fix is to make the device old and without access to backups, so that
we still consider this UTD unexpected.

crates/matrix-sdk-crypto/src/types/events/utd_cause.rs

@@ -162,7 +162,7 @@ mod tests {
         assert_eq!(
             UtdCause::determine(
                 &raw_event(json!({})),
-                device_new_with_backup(),
+                device_old_no_backup(),
                 &missing_megolm_session()
             ),
             UtdCause::Unknown