tests: Gracefully handle missing set_device for mps

[booxter]

What does this PR do?

mps backend doesn't have set_device, so if mps is available on test run,
the test fails with:

AttributeError: <module 'torch.mps' from
'[...]/site-packages/torch/mps/__init__.py'> does not have the attribute
'set_device'

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

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