Revert "Remove the fallback AddSupervisedUserActivity."

This reverts commit 86f350043905987fe950e1c197e1b27a8d9b73e5.

Reason for revert: Real flow is not ready yet, so we still need the fallback activity.

Change-Id: I34dc5386ff8c18a62b4b11e25fd355a62602329f
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 8b67880..e1a6595 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -2973,6 +2973,13 @@
         </activity>
 
         <activity
+            android:name=".users.AddSupervisedUserActivity"
+            android:label="@*android:string/supervised_user_creation_label"
+            android:icon="@drawable/ic_settings_multiuser"
+            android:exported="true">
+        </activity>
+
+        <activity
             android:name="Settings$PaymentSettingsActivity"
             android:label="@string/nfc_payment_settings_title"
             android:exported="true"