replace FrameLayout with merge tag

as a linter suggested

Bug: 325930922
Test: build
Change-Id: If80603437d7c0f87c7c21ea3fad4c9e8b88946d5
diff --git a/vmlauncher_app/res/layout/activity_main.xml b/vmlauncher_app/res/layout/activity_main.xml
index c588b19..e52dfcd 100644
--- a/vmlauncher_app/res/layout/activity_main.xml
+++ b/vmlauncher_app/res/layout/activity_main.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<merge xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
@@ -21,4 +21,4 @@
     <requestFocus />
   </SurfaceView>
 
-</FrameLayout>
+</merge>