fix: Remove incorrect background logic from PageLayoutGridLayout (#16945)

Removes the background color logic that was incorrectly added to
PageLayoutGridLayout in PR #16870. Grid layouts are only used for
dashboards where widgets have their own background colors set in
WidgetCard.tsx, so the container background was causing visual
mismatches in padding/gap areas. The background logic remains correctly
applied in PageLayoutVerticalListViewer and PageLayoutVerticalListEditor
where widgets need to inherit the container background.

---------

Co-authored-by: Devessier <baptiste@devessier.fr>

packages/twenty-front/src/modules/page-layout/components/PageLayoutVerticalListViewer.tsx

@@ -1,4 +1,4 @@
-import { useShouldUseWhiteBackground } from '@/page-layout/hooks/useShouldUseWhiteBackground';
+import { usePageLayoutShouldUseWhiteBackground } from '@/page-layout/hooks/usePageLayoutShouldUseWhiteBackground';
 import { type PageLayoutWidget } from '@/page-layout/types/PageLayoutWidget';
 import { WidgetRenderer } from '@/page-layout/widgets/components/WidgetRenderer';
 import styled from '@emotion/styled';
@@ -22,7 +22,7 @@ type PageLayoutVerticalListViewerProps = {
 export const PageLayoutVerticalListViewer = ({
   widgets,
 }: PageLayoutVerticalListViewerProps) => {
-  const { shouldUseWhiteBackground } = useShouldUseWhiteBackground();
+  const { shouldUseWhiteBackground } = usePageLayoutShouldUseWhiteBackground();
 
   return (
     <StyledVerticalListContainer