Move the wallpaper title string from ThemePicker to WallpaperPicker2.

        the home screen. [CHAR LIMIT=15] -->

    <string name="grid_title">Grid</string>

    <!-- Title of a section of the customization picker where the user can select a Wallpaper.

        [CHAR LIMIT=19] -->

    <string name="wallpaper_title">Wallpaper</string>

    <!-- Label for a button that allows the user to apply the currently selected Theme.

        [CHAR LIMIT=20] -->

    <string name="apply_theme_btn">Apply</string>