Don't include stretch overscroll in benchmark.

Fixes: 187219563

The benchmark watches the number of frames and the
stretch overscroll animation can affect the number
of frames that are produced.

Test: ran testSlowBindRecyclerViewFling
Change-Id: I90774980be850eda797fb80e655e7f4cd2dd76ac

tests/UiBench/res/layout/recycler_view.xml

@@ -17,5 +17,6 @@
 <androidx.recyclerview.widget.RecyclerView
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/recyclerView"
+    android:overScrollMode="never"
     android:layout_width="match_parent"
     android:layout_height="match_parent"/>