[kcmkwin/kwineffects] Collapse list item when clicking on it again

Currently, each effect's list items expands when you click on any
non-interactive part of it, but it does not collapse when you click on
it again.

With this commit, now it does.

BUG: 421883
FIXED-IN: 5.23

src/kcmkwin/kwineffects/package/contents/ui/Effect.qml

@@ -17,7 +17,13 @@ Kirigami.SwipeListItem {
     id: listItem
     hoverEnabled: true
     onClicked: {
-        view.currentIndex = index;
+        if (view.currentIndex == index) {
+            // Collapse list item
+            view.currentIndex = -1;
+        } else {
+            // Expand list item
+            view.currentIndex = index;
+        }
     }
     contentItem: RowLayout {
         id: row