[CI] Remove unittest dependency from testing_utils.py

[DN6]

What does this PR do?

Continue to remove unittest dependencies from tests.

Fixes # (issue)

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[sayakpaul]

Mostly nits.

[sayakpaul]

• Simpler (as torch_device will fail anyway so we won't need the first check)
• Easier to ready

Suggested change

	not (is_torch_available() and torch_device != "cpu"), reason="test requires accelerator+PyTorch"
	torch_device == "cpu", reason="test requires accelerator+PyTorch"

[sayakpaul]

Simpler and easier to read

Suggested change

	not (is_torch_available() and torch_device == "cuda"), reason="test requires PyTorch+CUDA"
	torch_device != "cuda", reason="test requires PyTorch+CUDA"