Improve test reliability for Accelerator.free_memory()

[matthewdouglas]

What does this PR do?

As discussed on Slack, this PR is intended to improve the reliability of a flaky unit test in accelerate/tests/test_accelerator.py @ AcceleratorTester.test_free_memory_dereferences_prepared_components.

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?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
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@muellerzr

[HuggingFaceDocBuilderDev]

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[muellerzr]

Nice find, computers are weird 🫤