Fix multiple divider when resize with rotate

When animatePendingSplitWithDisplayChange, we should update the
divider layout, but it used start transaction was already applied
by other handler, we should apply itself otherwise the previous
divider surface cannot be remove.

Fix: 286322573
Test: manual
Test: check winscope there is only one divider surface after repro
Test: pass existing tests
Change-Id: Ia4f44b474eda9bad4f5968a217a06a834c4bd542

libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageCoordinator.java

@@ -2500,6 +2500,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             if (mMixedHandler.animatePendingSplitWithDisplayChange(transition, info,
                     startTransaction, finishTransaction, finishCallback)) {
                 mSplitLayout.update(startTransaction);
+                startTransaction.apply();
                 return true;
             }
         }