fix: incorrect typing on return type

[stephantul]

The typing on the main query methods in vicinity was incorrect: it used the type used in the internal backends, i.e., a list of tuple of index, distance arrays. But Vicinity itself returns a list[list[str, float]] for both the normal query and query_threshold functions.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ
vicinity/vicinity.py	95.42% <100.00%> (-2.25%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Pringled]

LGTM ✨