Fix notification visibility when screensharing

Do not redact if notification marked as public visiblity and not
overridden by user channel visiblity

Bug: 324111564
Test: atest SensitiveNotificationProtectionControllerTest
Flag: ACONFIG com.android.server.notification.screenshare_notification_hiding DISABLED
Change-Id: Ib678f277f6422eb87d9cea11438d9d2e603064ca