Replace compile-time SIMD detection with Highway runtime target in vectorlite_info()

[Copilot]

The Highway runtime best target already supersedes the compile-time DetectSIMD() output. Remove the redundant "built with" string.

• Remove DetectSIMD() call and util.h include from sqlite_functions.cpp
• Simplify output format to: vectorlite extension version X.Y.Z. Best SIMD target in use: <target>
• Update docs in README.md and doc/markdown/api.md

select vectorlite_info();
-- Before: "vectorlite extension version 0.1.0, built with AVX. Best SIMD target in use: AVX2"
-- After:  "vectorlite extension version 0.1.0. Best SIMD target in use: AVX2"

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