Calling js SDK `authgear.promoteAnonymouserUser` in staging shows tabbed login/sign up screen, as opposed to the expected "Sign up to XXX" screen specifically for anonymous user

**Describe the bug**
As titled.

**Authgear Version**
- Version: SaaS on `authgear-staging` as of 2023-02-06.

**To Reproduce**
Steps to reproduce the behavior:
1. Setup an app in authgear portal
2. Setup a RN app and integrate with authgear
3. Create an anonymous user in app
5. Call `authgear.promoteAnonymousUser`
6. Observe the usual tabbed sign up/login screen is shown

**Expected behavior**
At (6), the "Sign up to XXX" screen for anonymous user is shown.

**Client Env (if applicable, please complete the following information):**
Not relevant as it's in mobile. Using RN SDK on pixel 6a, Android 13.

**Additional context**
N/A

Reproduce the flow in an Authgear staging app using a React Native app on Android: create an anonymous user and call authgear.promoteAnonymousUser. Trace the promotion and login screen flow from that entry point; done means the anonymous-user flow shows the “Sign up to XXX” screen instead of the usual tabbed login/sign-up screen.

Written by the indexing model from the issue text.