Update MIGRATION_GUIDE.md

Author: nan-li

MIGRATION_GUIDE.md

@@ -378,8 +378,9 @@ The Debug namespace is accessible via `OneSignal.Debug` and provide access to de
 
 - Changing app IDs is not supported.
 - Any `User` namespace calls must be invoked **after** initialization. Example: `OneSignal.User.addTag("tag", "2")`
+- In the SDK, the user state is only refreshed from the server when a new session is started (cold start or backgrounded for over 30 seconds) or when the user is logged in. This is by design.
 
 # Known issues
 
 - Identity Verification
-  - We will be introducing JWT in a follow-up release.
+  - We will be introducing Identity Verification using JWT in a follow up release