[Bugfix][Relay][Keras] Fix UpSampling2D about the wrong assertion about size

[jikechao]

This PR removed the wrong assertion about UpSampling2D.

In the Keras frontend of TVM, The UpSampling2D has a wired constraint: "Height must equal width for operator Upsample."

However, from the documentation about UpSampling2D, The constraint about size is, " Int, or tuple of 2 integers". Meanwhile, An official example from the Keras documentation uses the size(1, 2)
.

Thus, the assertion in TVM is wrong. I deleted the related statements and added a bug-triggering test case.

@echuraev @masahi @Hzfengsy

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• cc @shingjan _{See #10317 for details}

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