fix: Dont filter negative scores when using BM25Okapi and scale_score=False

[ZanSara]

Related Issues

• fixes #6801

Proposed Changes:

Add an exception in the InMemoryDocumentStore.bm25_retrieval() to not filter out negative values if the Okapi algorithm is used with scale_score=False, as such values are meaningful.

This PR also changes the default algorithm from BM25Okapi to BM25L to prevent the exception form being the default state of this Retriever. A few tests were adjusted as a consequence.

How did you test it?

Local tests

Notes for the reviewer

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 7797498811

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• 0 of 0 changed or added relevant lines in 0 files are covered.
• 252 unchanged lines in 30 files lost coverage.
• Overall coverage decreased (-0.7%) to 88.291%

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Files with Coverage Reduction	New Missed Lines	%
utils/auth.py	1	93.88%
components/websearch/searchapi.py	2	96.36%
components/builders/dynamic_chat_prompt_builder.py	3	93.02%
components/embedders/hugging_face_tei_document_embedder.py	3	95.24%
components/embedders/hugging_face_tei_text_embedder.py	3	92.86%
components/generators/hugging_face_local.py	3	96.0%
components/generators/hugging_face_tgi.py	3	95.4%
core/pipeline/descriptions.py	3	54.55%
components/embedders/sentence_transformers_document_embedder.py	4	90.7%
components/embedders/sentence_transformers_text_embedder.py	4	88.57%

Totals
Change from base Build 7743895092:	-0.7%
Covered Lines:	4728
Relevant Lines:	5355

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💛 - Coveralls

[silvanocerza]

Good to merge. 👍