docs: Clarified when you can put the fragments in the root view.

Per bug b/10641907, putting fragments in the root view *only* works
if the device runs Android 3.0 or later. Chris and Adam say
we don't really want to suggest that work flow even for these devices,
so I'm taking that info out.

bug: 10641907
Change-Id: Ie44acbb534b8e0cea8dbbfaaf2c65836b1c31be6

docs/html/guide/topics/ui/actionbar.jd

@@ -907,11 +907,7 @@ to ensure the best fit in the action bar.</p>
 <p>To get started, your layout must include a {@link android.view.ViewGroup} in which you place
 each {@link android.app.Fragment} associated with a tab. Be sure the {@link android.view.ViewGroup}
 has a resource ID so you can reference it from your code and swap the tabs within it.
-Alternatively, if the tab content will fill the activity layout, then your activity doesn't need a
-layout at all (you don't even need to call {@link android.app.Activity#setContentView
-setContentView()}). Instead, you can place each fragment in the default root view, which you can
-refer to with the {@code android.R.id.content} ID.</p>
-
+</p>
 
 <p>Once you determine where the fragments appear in the layout, the basic procedure to add tabs
 is:</p>