search: Drop SearchResultInterface again

It adds a significant cost to AppIcons which are used
 - quite a log (depending on installed apps)
 - in preformance-sensitive contexts (spring animation)

Just rely on duck typing and revert 91a5133116.

https://gitlab.gnome.org/GNOME/gnome-shell/issues/1799

js/ui/appDisplay.js

@@ -2045,7 +2045,6 @@ var AppFolderPopup = GObject.registerClass({
 
 var AppIcon = GObject.registerClass({
     GTypeName: 'AppDisplay_AppIcon',
-    Implements: [Search.SearchResultInterface],
     Signals: {
         'menu-state-changed': { param_types: [GObject.TYPE_BOOLEAN] },
         'sync-tooltip': {},