Make backport_s_notif_rules readable

Bug: 182313963
Test: atest
Change-Id: I4a0ba25a8a5f0674696a83e931ce2aa914c7e7ea
diff --git a/core/java/android/provider/Settings.java b/core/java/android/provider/Settings.java
index 2acf5f9..0c0dbf6 100644
--- a/core/java/android/provider/Settings.java
+++ b/core/java/android/provider/Settings.java
@@ -15801,6 +15801,7 @@
          * 1: Enabled (All apps will receive the new rules)
          * @hide
          */
+        @Readable
         public static final String BACKPORT_S_NOTIF_RULES = "backport_s_notif_rules";
 
         /**