Fix bubble button alignment

Set gravity of linear layout parent to "end"

Fixes: 159471266
Test: bubble button aligned right in LTR, left in RTL (w/ & w/o actions)
Change-Id: If15a70edca8aada3e2891758e15dc4a771099a04

core/res/res/layout/notification_material_action_list.xml

@@ -25,6 +25,7 @@
             android:id="@+id/actions_container_layout"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
+            android:gravity="end"
             android:orientation="horizontal"
             android:paddingEnd="@dimen/bubble_gone_padding_end"
             >