Remove view index adjustment for retry button (which no longer exists)

Issue: #4059

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=191414566

demos/main/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java

@@ -550,7 +550,7 @@ public class PlayerActivity extends Activity
         button.setText(label);
         button.setTag(i);
         button.setOnClickListener(this);
-        debugRootView.addView(button, debugRootView.getChildCount() - 1);
+        debugRootView.addView(button);
       }
     }
   }