DataGrid - FilterRow cell in the 'buttons' column is white in the fluent dark theme in the Application Template (T1275734) (DevExpress#29294)

Author: tongsonbarbs

packages/devextreme-scss/scss/widgets/fluent/gridBase/_colors.scss

@@ -190,6 +190,7 @@ $datagrid-icon-link-disabled-opacity: $button-disabled-icon-opacity;
 
 @if $mode == "dark" {
   $datagrid-row-focused-bg: #0c3b5e !default;
+  $datagrid-filter-row-background-color: lighten($datagrid-base-background-color, 2%) !default;
   $datagrid-columnchooser-item-color: color.change($datagrid-base-color, $alpha: 0.6) !default;
   $datagrid-group-row-color: $datagrid-columnchooser-item-color !default;
   $datagrid-block-separator-bg: lighten($datagrid-base-background-color, 12%) !default;