Don't set a background color for scrollable preview.

It had an old value and wasn't needed anyway.

Bug: 280479440
Test: Visual verification of correct color shade.
Change-Id: Id0707f5b3332e95cd8a561a3e9bb2f7676d6ee20
diff --git a/java/res/layout/chooser_grid_preview_image.xml b/java/res/layout/chooser_grid_preview_image.xml
index 20c4978..4d46241 100644
--- a/java/res/layout/chooser_grid_preview_image.xml
+++ b/java/res/layout/chooser_grid_preview_image.xml
@@ -34,7 +34,6 @@
         android:layout_gravity="center_horizontal"
         android:layout_marginBottom="@dimen/chooser_view_spacing"
         android:layout_marginHorizontal="@dimen/chooser_edge_margin_normal_half"
-        android:background="?android:attr/colorBackground"
         app:itemInnerSpacing="3dp"
         app:itemOuterSpacing="@dimen/chooser_edge_margin_normal_half"/>