test(mge/test_save_load): remove test model file

GitOrigin-RevId: 893b82b1c93b07e778310799b78b822e8eaa4246

imperative/python/test/integration/test_save_load.py

+# MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+import os
+
 import numpy as np
 
 import megengine as mge
@@ -53,6 +62,7 @@ def test_save_load():
     optim = optimizer.SGD(net.parameters(), lr=1.0, momentum=0.9)
     optim.load_state_dict(checkpoint["opt_state"])
     print("load done")
+    os.remove("simple.pkl")
 
     with gm:
         loss = net([1.23])