fix(deps): update rust crate git2 to 0.20.4

[xtqqczze]

Crate:     git2
Version:   0.20.2
Warning:   unsound
Title:     Potential undefined behavior when dereferencing Buf struct
Date:      2026-02-02
ID:        RUSTSEC-2026-0008
URL:       https://rustsec.org/advisories/RUSTSEC-2026-0008

[codspeed-hq]

Merging this PR will not alter performance

✅ 4 untouched benchmarks

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_{Comparing xtqqczze:deps/git2 (7d96d5b) with main (be3c3b2)}