Add a11y announcement

Since the button for clearing recent conversations may still
exist after the user triggers the button since some of the
conversations might not be removable

Test: manual with talkback
Fixes: 185433664
Change-Id: Id58d76237643e4e206ea6d551cdf7dd9f5742282

src/com/android/settings/notification/app/RecentConversationsPreferenceController.java

@@ -92,6 +92,7 @@ public class RecentConversationsPreferenceController extends AbstractPreferenceC
                         }
                     }
                 }
+                button.announceForAccessibility(mContext.getString(R.string.recent_convos_removed));
             } catch (RemoteException e) {
                 Slog.w(TAG, "Could not clear recents", e);
             }