Remove unused strings

    <!-- Title of the notification when guest mode is entered [CHAR LIMIT=35] -->

    <string name="guest_notification_session_active">You are in guest mode</string>

    <!-- Title for add user confirmation dialog [CHAR LIMIT=30] -->

    <string name="user_add_user_title" msgid="2108112641783146007">Add new user?</string>

    <!-- Message for add user confirmation dialog - short version. [CHAR LIMIT=none] -->

    <string name="user_add_user_message_short" msgid="1511354412249044381">When you add a new user, that person needs to set up their space.\n\nAny user can update apps for all other users. </string>

    <!-- Additional message for add user confirmation dialog that is appended when current user is

         guest and guest is ephemeral. This is to warn users that current guest session

         would get removed after a new user is added and switched to [CHAR LIMIT=none] -->