overview: Clean up dead code

These unused functions accessed undefined functions on a now undefined
variable/class. This vestigial code can go away.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1643>

js/ui/overview.js

@@ -115,10 +115,6 @@ class OverviewActor extends St.BoxLayout {
         return this._controls.searchEntry;
     }
 
-    get viewSelector() {
-        return this._controls.viewSelector;
-    }
-
     get controls() {
         return this._controls;
     }
@@ -249,14 +245,6 @@ var Overview = class {
         this._swipeTracker = swipeTracker;
     }
 
-    addSearchProvider(provider) {
-        this._overview.viewSelector.addSearchProvider(provider);
-    }
-
-    removeSearchProvider(provider) {
-        this._overview.viewSelector.removeSearchProvider(provider);
-    }
-
     //
     // options:
     //  - undoCallback (function): the callback to be called if undo support is needed