fix: Correct parameter name for faithfulness evaluator and fix component names passed to PipelinePair

[shadeMe]

Proposed Changes:

Fixes:

• The parameter name for the faithfulness evaluator was outdated.
• The meta names of the expected components were incorrectly being passed to the to PipelinePair instead of the component names.

How did you test it?

All tests

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 9513555861

Details

• 20 of 22 (90.91%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.764%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	20	22	90.91%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

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💛 - Coveralls