Update Build#SERIAL docs about deprecation policy

Test: docs only change

Change-Id: Ic9738764b0d18056401fcd103bfaf95a1701981d
diff --git a/core/java/android/os/Build.java b/core/java/android/os/Build.java
index 935f5f3..6ebf3b9 100644
--- a/core/java/android/os/Build.java
+++ b/core/java/android/os/Build.java
@@ -103,7 +103,7 @@
 
     /**
      * A hardware serial number, if available. Alphanumeric only, case-insensitive.
-     * For apps targeting SDK higher than {@link Build.VERSION_CODES#N_MR1} this
+     * For apps targeting SDK higher than {@link Build.VERSION_CODES#O_MR1} this
      * field is set to {@link Build#UNKNOWN}.
      *
      * @deprecated Use {@link #getSerial()} instead.