chore(pivot): revert removed @output

Author: dkamburov

projects/igniteui-angular/src/lib/grids/pivot-grid/pivot-data-selector.component.ts

@@ -107,7 +107,6 @@ export class IgxPivotDataSelectorComponent {
     @Input({ transform: booleanAttribute })
     public columnsExpanded = true;
 
-    /**
     /**
      * Emitted when the columns panel is expanded or collapsed.
      *
@@ -210,6 +209,7 @@ export class IgxPivotDataSelectorComponent {
      *              (valuesExpandedChange)="valuesExpandedChange($event)"></igx-pivot-data-selector>
      * ```
     */
+    @Output()
     public valuesExpandedChange = new EventEmitter<boolean>();
 
     private _grid: PivotGridType;