Enable 3 button nav for taskbar

Bug: 180046394
Test: Switched between gesture and button nav on
phone and tablet.

Change-Id: Iac2357a3256f8b6b36ca49d3680594a91e824a5f

quickstep/src/com/android/launcher3/taskbar/TaskbarControllers.java

@@ -61,7 +61,7 @@ public class TaskbarControllers {
      */
     public void init() {
         navbarButtonsViewController.init(this);
-        if (taskbarActivityContext.canShowNavButtons()) {
+        if (taskbarActivityContext.isThreeButtonNav()) {
             rotationButtonController.init();
         }
         taskbarDragLayerController.init(this);