[TabUI] Remove unused variable in tests

Bug: 937678
Change-Id: I099f47df0f3682bb8baec1fe6e472cc2e2ee8a9e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1773320Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Auto-Submit: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691152}

chrome/android/features/tab_ui/javatests/src/org/chromium/chrome/browser/tasks/tab_management/TabListContainerViewBinderTest.java

@@ -54,7 +54,6 @@ public class TabListContainerViewBinderTest extends DummyUiActivityTestCase {
     public TestRule mProcessor = new Features.JUnitProcessor();
 
     private static final int CONTAINER_HEIGHT = 56;
-    private TabListContainerViewBinder mTabListContainerViewHolder;
     private PropertyModel mContainerModel;
     private PropertyModelChangeProcessor mMCP;
     private TabListRecyclerView mRecyclerView;