[Statsig] Mark Testflight as staging tier (#3470)

src/lib/statsig/statsig.tsx

@@ -9,6 +9,7 @@ import {
 } from 'statsig-react-native-expo'
 
 import {logger} from '#/logger'
+import {IS_TESTFLIGHT} from 'lib/app-info'
 import {useSession} from '../../state/session'
 import {LogEvents} from './events'
 import {Gate} from './gates'
@@ -17,7 +18,12 @@ export type {LogEvents}
 
 const statsigOptions = {
   environment: {
-    tier: process.env.NODE_ENV === 'development' ? 'development' : 'production',
+    tier:
+      process.env.NODE_ENV === 'development'
+        ? 'development'
+        : IS_TESTFLIGHT
+        ? 'staging'
+        : 'production',
   },
   // Don't block on waiting for network. The fetched config will kick in on next load.
   // This ensures the UI is always consistent and doesn't update mid-session.