chore(deps): bump git2 from 0.20.4 to 0.21.0

Bumps [git2](https://github.com/rust-lang/git2-rs) from 0.20.4 to 0.21.0.
- [Changelog](https://github.com/rust-lang/git2-rs/blob/main/CHANGELOG.md)
- [Commits](rust-lang/git2-rs@git2-0.20.4...git2-0.21.0)

---
updated-dependencies:
- dependency-name: git2
  dependency-version: 0.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Cargo.lock

@@ -23,7 +23,7 @@ clap = { version = "4.6", features = ["derive"] }
 # integration is deferred until the Rust↔AffineScript bridge exists (ADR-006);
 # it will be re-added as a git/published dep (not a path dep) when that lands.
 reqwest = { version = "0.13", features = ["json"], optional = true }
-git2 = { version = "0.20", optional = true }               # Git repo parsing
+git2 = { version = "0.21", optional = true }               # Git repo parsing
 postgres = { version = "0.19", features = ["with-uuid-1"], optional = true }
 tch = { version = "0.24", optional = true }                 # PyTorch embeddings