Remove "public" to follow our convention

Change-Id: Ic5fa8744cbcb4c704780c8467ae0f31fce3327ce
diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupKey.java b/core/api/src/main/java/org/onosproject/net/group/GroupKey.java
index 9c87b83..a63bee2 100644
--- a/core/api/src/main/java/org/onosproject/net/group/GroupKey.java
+++ b/core/api/src/main/java/org/onosproject/net/group/GroupKey.java
@@ -27,5 +27,5 @@
      *
      * @return byte array
      */
-    public byte[] key();
+    byte[] key();
 }