Notifications: Fix the undo dismiss button (#97850)

* Position the dismiss button correctly, and only close the undo notification.

* Remove unnecessary styling.

* Stop event propagation instead of using a new function.

apps/notifications/src/panel/boot/stylesheets/main.scss

@@ -579,6 +579,8 @@ $with-sidebar-min-page-width: 1114px;
 		p {
 			padding-top: 1em;
 			padding-bottom: 1em;
+			display: flex;
+			align-items: center;
 		}
 
 		.wpnc__undo-link {
@@ -594,8 +596,8 @@ $with-sidebar-min-page-width: 1114px;
 
 	.wpnc__close-link {
 		color: var(--color-text-inverted);
-		position: absolute;
-		right: 10px;
+		margin-left: auto;
+		padding: 0 10px;
 		cursor: pointer;
 		user-select: none;
 	}

apps/notifications/src/panel/templates/undo-list-item.jsx

@@ -132,8 +132,9 @@ export class UndoListItem extends Component {
 	};
 
 	actImmediately = ( event ) => {
-		if ( event && event.preventDefault ) {
+		if ( event ) {
 			event.preventDefault();
+			event.stopPropagation();
 		}
 		clearTimeout( this.state.undoTimer );
 		this.instance && this.setState( { isVisible: false } );