Install peft from main for CI tests with dev dependencies

[albertvillanova]

Install peft from main for CI tests with dev dependencies.

This PR updates the CI tests with dev dependencies and aligns peft with the rest of the Hugging Face libraries, installing its dev version from the GH repo main branch.

Additionally, this PR fixes the CI AttributeError: type object 'DynamicCache' has no attribute 'from_legacy_cache': the fix is already on peft main branch:

• Replace from_legacy_cache method with constructors  peft#2767

Fix #4248.

[HuggingFaceDocBuilderDev]

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[qgallouedec]

okay, lgtm. peft is an optional dependency, but since it is widely used, I think it makes sense to test it here with dev.

[albertvillanova]

Yes, and also note that before this PR it was already installed, but not from main branch repo, but latest stable version:

trl/pyproject.toml

Lines 103 to 104 in f853e09

	# peft
	"peft>=0.8.0",