DeskClock: Use sans-serif-thin font for the clock widget

<resources>

    <style name="widget_big_thin" parent="big_thin">

        <item name="android:fontFamily">sans-serif-light</item>

        <item name="android:fontFamily">sans-serif-thin</item>

        <item name="android:shadowRadius">@dimen/widget_shadow_radius</item>

        <item name="android:shadowColor">@color/widget_shadow_color</item>

        <item name="android:shadowDx">@dimen/widget_shadow_dx</item>