Don't animate the workspace background alpha during recents anim

This is somewhat expensive and could cause jank

Change-Id: I75c2e957781c865e8d275ecc083e5edfa31e04d3
diff --git a/quickstep/src/com/android/launcher3/LauncherAppTransitionManagerImpl.java b/quickstep/src/com/android/launcher3/LauncherAppTransitionManagerImpl.java
index 8f498d2..68f6667 100644
--- a/quickstep/src/com/android/launcher3/LauncherAppTransitionManagerImpl.java
+++ b/quickstep/src/com/android/launcher3/LauncherAppTransitionManagerImpl.java
@@ -16,7 +16,6 @@
 
 package com.android.launcher3;
 
-import static com.android.launcher3.LauncherAnimUtils.DRAWABLE_ALPHA;
 import static com.android.launcher3.allapps.AllAppsTransitionController.ALL_APPS_PROGRESS;
 import static com.android.systemui.shared.recents.utilities.Utilities.getNextFrameNumber;
 import static com.android.systemui.shared.recents.utilities.Utilities.getSurface;
@@ -323,9 +322,6 @@
         launcherAnimator.play(recenterWorkspace);
         CellLayout currentWorkspacePage = (CellLayout) workspace.getPageAt(
                 workspace.getCurrentPage());
-        Animator hideWorkspaceScrim = ObjectAnimator.ofInt(
-                currentWorkspacePage.getScrimBackground(), DRAWABLE_ALPHA, 0);
-        launcherAnimator.play(hideWorkspaceScrim);
 
         launcherAnimator.setInterpolator(Interpolators.TOUCH_RESPONSE_INTERPOLATOR);
         launcherAnimator.setDuration(RECENTS_LAUNCH_DURATION);