chore: Hide HF unauthenticated warning

[Pringled]

We currently show the following warning on the first use of semble because we download potion code from HF hub:

"Warning: You are sending unauthenticated requests to the HF Hub. "
            "Please set a HF_TOKEN to enable higher rate limits and faster downloads.",

This PR hides that since the model downloads fine without it and it only adds confusion. The useful errors if anything actually goes wrong are still shown.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
src/semble/index/dense.py	100.00% <100.00%> (ø)

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[greptile-apps]

Confidence Score: 4/5

The PR appears safe to merge, though narrowing the filter would prevent unrelated token diagnostics from being suppressed.

_{Reviews (1) · Last reviewed commit: "test: Use exact Hub warning text in HF_T..."}

[stephantul]

Aside from the greptile comment (I think you could make the filter even more specific?) this is fine.