Refine test_label_semantic_roles of Fluid (#7193)

Author: ranqiu92

python/paddle/v2/fluid/tests/book/test_label_semantic_roles.py

@@ -34,7 +34,7 @@
 
 IS_SPARSE = True
 PASS_NUM = 10
-BATCH_SIZE = 20
+BATCH_SIZE = 10
 
 embedding_name = 'emb'