Update sticky section (WordPress#51274)

Author: jameskoster

packages/edit-site/src/components/sidebar-navigation-screen/style.scss

@@ -12,7 +12,6 @@
 }
 
 .edit-site-sidebar-navigation-screen__content {
-	margin: 0 0 $grid-unit-20 0;
 	color: $gray-400;
 	padding: 0 $grid-unit-20;
 	.components-item-group {
@@ -88,9 +87,10 @@
 	bottom: 0;
 	background-color: $gray-900;
 	gap: 0;
-	padding: $grid-unit-40 0;
-	margin: $grid-unit-40 $grid-unit-20;
+	padding: $grid-unit-20 0;
+	margin: $grid-unit-20 0 0;
 	border-top: 1px solid $gray-800;
+	box-shadow: 0 #{-$grid-unit-10} $grid-unit-20 $gray-900;
 }
 
 .edit-site-sidebar-navigation-screen__footer {