fix typo

Author: ZHUI

pgl/tests/test_graph_saint_sample.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
+# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -22,7 +22,7 @@
 
 
 class GraphSaintSampleTest(unittest.TestCase):
-    """ScatterAddTest"""
+    """GraphSaintSampleTest"""
 
     def test_randomwalk_sampler(self):
         """test_scatter_add"""