A11y changes for notification controller of switch

This CL aims at making a11y changes for notification controller switch
in the wallpaper picker. We added a content description so we announce
the right description when the switch is focussed.

Bug: b/280748132
Test: Tested by building and installing picker on local, and checking
the talkback service. Video attached in bug.

Change-Id: Ifd48ee406a4bafbcf3da208d8f5e49b97be55e7a
diff --git a/res/layout/notification_section.xml b/res/layout/notification_section.xml
index f490e00..3e29a4e 100644
--- a/res/layout/notification_section.xml
+++ b/res/layout/notification_section.xml
@@ -39,6 +39,7 @@
         android:id="@+id/switcher"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
+        android:focusable="false"
         android:clickable="false"
         android:layout_gravity="center"
         style="@style/Switch.SettingsLib"