Bumped version of gRPC to 1.3.1

Change-Id: I7798476bd443a796e0e6a6e149ab8f66435ba4fa
diff --git a/apps/p4runtime-test/BUCK b/apps/p4runtime-test/BUCK
index 521f7c2..d81fd06 100644
--- a/apps/p4runtime-test/BUCK
+++ b/apps/p4runtime-test/BUCK
@@ -1,4 +1,4 @@
-GRPC_VER = '1.3.0'
+GRPC_VER = '1.3.1'
 PROTOBUF_VER = '3.2.0'
 
 COMPILE_DEPS = [