remove redundant codes in ModuleDict

[Flowingsun007]

fix module.py的ModuleDict类中的重复多余代码，某些情况下会导致bug：https://github.com/Oneflow-Inc/OneTeam/issues/544

[daquexian]

测试是不是可以简单一些，如果没有什么实际内容，只是两个 relu module 组成的 dict 呢

[github-actions]

CI failed, removing label automerge

[github-actions]

Speed stats:

GPU Name: GeForce GTX 1080 

PyTorch resnet50 time: 139.4ms (= 6971.9ms / 50, input_shape=[16, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 128.4ms (= 6418.9ms / 50, input_shape=[16, 3, 224, 224], backward is enabled)
Relative speed: 1.09 (= 139.4ms / 128.4ms)

PyTorch resnet50 time: 84.8ms (= 4237.9ms / 50, input_shape=[8, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 74.8ms (= 3741.1ms / 50, input_shape=[8, 3, 224, 224], backward is enabled)
Relative speed: 1.13 (= 84.8ms / 74.8ms)

PyTorch resnet50 time: 59.6ms (= 2977.8ms / 50, input_shape=[4, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 47.8ms (= 2389.7ms / 50, input_shape=[4, 3, 224, 224], backward is enabled)
Relative speed: 1.25 (= 59.6ms / 47.8ms)

PyTorch resnet50 time: 48.8ms (= 2439.8ms / 50, input_shape=[2, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 38.2ms (= 1909.9ms / 50, input_shape=[2, 3, 224, 224], backward is enabled)
Relative speed: 1.28 (= 48.8ms / 38.2ms)

PyTorch resnet50 time: 44.6ms (= 2231.5ms / 50, input_shape=[1, 3, 224, 224], backward is enabled)
OneFlow resnet50 time: 36.6ms (= 1827.6ms / 50, input_shape=[1, 3, 224, 224], backward is enabled)
Relative speed: 1.22 (= 44.6ms / 36.6ms)