altTab: Remove override of _itemEnteredHandler()

This override function is identical to the original function, so remove
it.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2097>

js/ui/altTab.js

@@ -242,10 +242,6 @@ class AppSwitcherPopup extends SwitcherPopup.SwitcherPopup {
             this._select(n);
     }
 
-    _itemEnteredHandler(n) {
-        this._select(n);
-    }
-
     _windowActivated(thumbnailSwitcher, n) {
         let appIcon = this._items[this._selectedIndex];
         Main.activateWindow(appIcon.cachedWindows[n]);