change background of AlertDialog

Fixes: 111504032

Change-Id: If5125d64ce1a7ff6aa6c2c0a56ce3d76593158e3
Test: manually
diff --git a/car_product/overlay/frameworks/base/core/res/res/layout/alert_dialog_material.xml b/car_product/overlay/frameworks/base/core/res/res/layout/alert_dialog_material.xml
index a302a5d..0298cce 100644
--- a/car_product/overlay/frameworks/base/core/res/res/layout/alert_dialog_material.xml
+++ b/car_product/overlay/frameworks/base/core/res/res/layout/alert_dialog_material.xml
@@ -21,6 +21,7 @@
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:gravity="start|top"
+    android:background="@color/car_card"
     android:orientation="vertical">
 
     <include layout="@layout/alert_dialog_title_material" />