Remove peft tests from old lora backend tests

[DN6]

What does this PR do?

Currently the test_lora_layers_peft.py file is being executed in the old lora backend runner. This is causing some confusion when looking at CI results. This PR changes it so that PEFT tests do not run in the old lora backend runner.

Fixes # (issue)

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[HuggingFaceDocBuilderDev]

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[sayakpaul]

Thanks!