Fix quickstart mlp (#332)

* Edition of changing eval to test

* first fix of issue 313

* startup

* demo of quickstart

* Fix of quickstart

* remove extra files

* revert cn/mkdocs.yml

* use master cn/mkdocs.yml

* fix
Co-authored-by: Nunknown <liuqi0108@outlook.com>

cn/docs/code/quick_start/mlp_mnist.py

 # mlp_mnist.py
-import oneflow as flow
-import oneflow.typing as tp
+from oneflow.compatible import single_client as flow
+from oneflow.compatible.single_client import typing as tp
 import numpy as np
 
 flow.config.enable_legacy_model_io(False)