Fix unused variable warning (#32616)

test/cpp/util/channel_trace_proto_helper.cc

@@ -56,7 +56,8 @@ void VaidateProtoJsonTranslation(const std::string& json_str) {
   // We usually do not want this to be true, however it can be helpful to
   // uncomment and see the output produced then all fields are printed.
   // print_options.always_print_primitive_fields = true;
-  s = grpc::protobuf::json::MessageToJsonString(msg, &proto_json_str);
+  s = grpc::protobuf::json::MessageToJsonString(msg, &proto_json_str,
+                                                print_options);
   EXPECT_TRUE(s.ok());
   // Parse JSON and re-dump to string, to make sure formatting is the
   // same as what would be generated by our JSON library.