Fix Tapl Background.switchToOverview for tablets

- The test failed because of unexpected touch event recoreded
- This is because it does not expect the gesture to start from launcher. But with taskbar present, the touch will be recorded from taskbar

Bug: 191344757
Test: TaplTestsQuickStep
Change-Id: I09b5a3029eef5cdc874bbbe8653976f12136144c
diff --git a/tests/tapl/com/android/launcher3/tapl/Background.java b/tests/tapl/com/android/launcher3/tapl/Background.java
index 55be593..809e3ed 100644
--- a/tests/tapl/com/android/launcher3/tapl/Background.java
+++ b/tests/tapl/com/android/launcher3/tapl/Background.java
@@ -68,7 +68,7 @@
     }
 
     protected boolean zeroButtonToOverviewGestureStartsInLauncher() {
-        return false;
+        return mLauncher.isTablet();
     }
 
     protected void goToOverviewUnchecked() {