Allow mmh3 5.x (widen to >=4.1.0,<6.0.0)

[MiguelAmorimMP]

What

Widens the mmh3 constraint from ^4.1.0 (which caps at <5.0.0) to >=4.1.0,<6.0.0, so projects depending on pinecone-text can adopt mmh3 5.x. mmh3 4.x remains fully supported — nothing is dropped.

Why

mmh3 5.x has been the current major since late 2024, and this package's caret pin is (in our dependency tree at least) the only thing holding downstream projects on 4.x — pip resolution fails outright for pinecone-text==0.11.0 + mmh3>=5. Same situation as the mmh3 3→4 transition, which was resolved by widening the range (#76).

Safety

• The only mmh3 call in the package is mmh3.hash(token, signed=False) in pinecone_text/sparse/bm25_encoder.py.
• MurmurHash3 output is algorithm-fixed: I verified mmh3.hash(t, signed=False) returns bit-identical values on 4.1.0 and 5.2.1 for ASCII and non-ASCII tokens — so existing BM25 sparse indexes are unaffected by the wider range.
• tests/unit/test_bm25.py + tests/unit/test_bm25_tokenizer.py: 21 passed with mmh3 5.2.1 installed (Python 3.12).

The 5.x line is API/packaging modernisation (new buffer-protocol APIs, wheels for newer CPython); the hash() signature used here is unchanged.

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Note

Low Risk
Only the Poetry dependency constraint changes; runtime hashing behavior is unchanged and mmh3 4.x stays supported.

Overview
Dependency-only change: pyproject.toml relaxes the mmh3 pin from ^4.1.0 (effectively <5.0.0) to >=4.1.0,<6.0.0, so installs can resolve mmh3 5.x alongside pinecone-text while 4.x remains allowed.

No library code changes. BM25 sparse encoding still uses mmh3.hash(token, signed=False) in bm25_encoder.py; widening the declared range does not alter that call site.

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