Add divider line in Multiple users screen

Add a divider line above "Add users from lock screen" setting in "Multiple users" section.

Bug: 74799260
Test: Robotest and manual test
Change-Id: I69bae7a8e8a825634bda8b8d19230fe189cc4d4c

res/xml/user_settings.xml

@@ -16,6 +16,7 @@
 
 <PreferenceScreen
     xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:settings="http://schemas.android.com/apk/res-auto"
     android:key="user_settings_screen"
     android:title="@string/user_settings_title">
 
@@ -35,6 +36,7 @@
         android:key="user_settings_add_users_when_locked"
         android:title="@string/user_add_on_lockscreen_menu"
         android:singleLineTitle="false"
-        android:order="105"/>
+        android:order="105"
+        settings:allowDividerAbove="true"/>
 
 </PreferenceScreen>