Move EXTRA_SUBSTITUTE_APP_NAME to the published system api.

Bug: 26517701
Change-Id: I27000d777247c598cc509079004b4506ef05b404
diff --git a/core/java/android/app/Notification.java b/core/java/android/app/Notification.java
index dd05392..0a873d9 100644
--- a/core/java/android/app/Notification.java
+++ b/core/java/android/app/Notification.java
@@ -976,10 +976,8 @@
      */
     public static final String EXTRA_CONTAINS_CUSTOM_VIEW = "android.contains.customView";
 
-    /**
-     * @SystemApi
-     * @hide
-     */
+    /** @hide */
+    @SystemApi
     public static final String EXTRA_SUBSTITUTE_APP_NAME = "android.substName";
 
     private Icon mSmallIcon;