Fix missing border in the quick inserter. (#35307)

* Fix missing border in the quick inserter.

In the quick inserter, when no search results are found, there is some left/right border missing. This is caused by some margin applied to the `block-editor-inserter__no-results` div. While this margin could just be removed, I feel it is easier to just apply `overflow: hidden` to the container element. That way the spacing is preserved and should prevent any future issues.

* Update style.scss

Remove top margin and revert previous change.

packages/block-editor/src/components/inserter/style.scss

@@ -191,7 +191,6 @@ $block-inserter-tabs-height: 44px;
 
 .block-editor-inserter__no-results {
 	padding: $grid-unit-40;
-	margin-top: $grid-unit-40 * 2;
 	text-align: center;
 }