Use torch.testing.assert_close everywhere

[otaj]

What does this PR do?

In the PR #13123 (comment), we introduced a convention of checking for version to use torch-version-appropriate function for checking closeness of tensors. However, according to pytorch/pytorch#61844, the torch.testing.assert_close was introduced in 1.9, therefore we should be able to call it in all versions we currently support.

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None

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