Revert "Update dialog background color for dark theme"

This reverts commit 3032628269.

Reason for revert: This will also change the background color of other components within dialog.

Bug: 132753127
Bug: 132623454
Test: visual
Change-Id: I59d4731e84e8d516a01780c4cce70b2d86208098

res/values-night/colors.xml

@@ -22,8 +22,6 @@
     <color name="homepage_card_dismissal_background">@*android:color/material_grey_900</color>
     <color name="contextual_card_background">@*android:color/material_grey_900</color>
     <color name="search_bar_background">@*android:color/material_grey_800</color>
-    <!-- Dialog background color -->
-    <color name="dialog_background">@*android:color/material_grey_800</color>
     <color name="notification_importance_selection_bg">@*android:color/material_grey_800</color>
     <color name="notification_importance_button_selected">#AECBFA</color> <!-- material blue 200 -->
     <color name="notification_importance_button_unselected">#5F6368</color>

res/values-night/themes.xml

@@ -33,7 +33,6 @@
 
     <style name="Theme.AlertDialog.Base" parent="@style/Theme.AppCompat.DayNight.Dialog.Alert">
         <item name="colorAccent">@*android:color/accent_device_default_dark</item>
-        <item name="android:background">@color/dialog_background</item>
     </style>
 
 </resources>

res/values/colors.xml

@@ -144,7 +144,4 @@
     <!-- Search bar background color -->
     <color name="search_bar_background">@android:color/white</color>
 
-    <!-- Dialog background color -->
-    <color name="dialog_background">@*android:color/background_device_default_light</color>
-
 </resources>

res/values/themes.xml

@@ -121,7 +121,6 @@
 
     <style name="Theme.AlertDialog.Base" parent="@style/Theme.AppCompat.DayNight.Dialog.Alert">
         <item name="colorAccent">@*android:color/accent_device_default_light</item>
-        <item name="android:background">@color/dialog_background</item>
     </style>
 
     <style name="Theme.AlertDialog" parent="Theme.AlertDialog.Base">