Bump git2 from 0.16.1 to 0.18.0

Bumps [git2](https://github.com/rust-lang/git2-rs) from 0.16.1 to 0.18.0.
- [Changelog](https://github.com/rust-lang/git2-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/git2-rs/compare/0.16.1...git2-0.18.0)

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

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

Cargo.toml

@@ -66,7 +66,7 @@ walkdir = { version = "2.3", optional = true }
 bytesize = { version = "1.2.0" }
 
 [dependencies.git2]
-version = "0.16"
+version = "0.18"
 optional = true
 default-features = false