Fix GridDetailsLayoutExpandTest (#8556)

uitest/src/main/java/com/vaadin/tests/components/grid/GridDetailsLayoutExpand.java

 
         grid.setDetailsGenerator(item -> {
             final HorizontalLayout detailsLayout = new HorizontalLayout();
+            detailsLayout.setSpacing(false);
             detailsLayout.setSizeFull();
             detailsLayout.setHeightUndefined();
 
             // layout2 second element of the detailsLayout, taking the rest
             // of the available space
             final HorizontalLayout layout2 = new HorizontalLayout();
+            layout2.setSpacing(false);
             layout2.setSizeFull();
             layout2.setHeightUndefined();
             detailsLayout.addComponent(layout2);