fix: include factor_id in query (supabase#1702)

## What kind of change does this PR introduce?
* `FixLatestUnexpiredChallenge` should be scoped to the `factor_id` and
not all challenges in the table

## What is the current behavior?

Please link any relevant issues here.

## What is the new behavior?

Feel free to include screenshots if it includes visual changes.

## Additional context

Add any other context or screenshots.

internal/models/factor.go

@@ -300,7 +300,7 @@ func (f *Factor) FindLatestUnexpiredChallenge(tx *storage.Connection, expiryDura
 	var challenge Challenge
 	expirationTime := now.Add(time.Duration(expiryDuration) * time.Second)
 
-	err := tx.Where("sent_at > ?", expirationTime).
+	err := tx.Where("sent_at > ? and factor_id = ?", expirationTime, f.ID).
 		Order("sent_at desc").
 		First(&challenge)