Hide taskbar background when notification shade is expanded

- In 3 button mode, don't hide the background but do ensure nav buttons are translated down when swiping to notificaitons from the home screen

Test: swipe down notifications, background hides in 0 button mode but not in 3 button mode
Fixes: 199163951
Change-Id: Ic70adc7d67b2ab7c92a2d5d846b9b259d1bd7bfc

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

@@ -115,16 +115,6 @@ public class TaskbarViewController {
         mTaskbarView.setTouchesEnabled(!isImeVisible);
     }
 
-    /**
-     * Should be called when the notification shade is expanded, so we can hide taskbar icons as
-     * well. Note that we are animating icons to appear / disappear.
-     */
-    public void setNotificationShadeIsExpanded(boolean isNotificationShadeExpanded) {
-        mTaskbarIconAlpha.getProperty(ALPHA_INDEX_NOTIFICATION_EXPANDED)
-                .animateToValue(isNotificationShadeExpanded ? 0 : 1)
-                .start();
-    }
-
     /**
      * Should be called when the recents button is disabled, so we can hide taskbar icons as well.
      */