Update adv.filtering styling snippet to use query builder vars. (#1816)

Co-authored-by: Martin Dragnev <[email protected]>

Author: MayaKirova

doc/en/components/grids/_shared/advanced-filtering.md

@@ -609,8 +609,12 @@ Then set the related CSS properties to this class:
 
 ```css
 .grid {
-    --ig-grid-filtering-row-background: #ffcd0f;
-    --ig-grid-filtering-background-or: #d83434;
+    --ig-query-builder-header-foreground: #512da8;
+    --ig-query-builder-color-expression-group-and: #eb0000;
+    --ig-query-builder-color-expression-group-or: #0000f3;
+    --ig-query-builder-subquery-header-background: var(--ig-gray-300);
+    --ig-query-builder-subquery-border-color: var(--ig-warn-500);
+    --ig-query-builder-subquery-border-radius: 4px;
 }
 ```