Bump git2 from 0.20.2 to 0.20.4

Bumps [git2](https://github.com/rust-lang/git2-rs) from 0.20.2 to 0.20.4.
- [Changelog](https://github.com/rust-lang/git2-rs/blob/git2-0.20.4/CHANGELOG.md)
- [Commits](rust-lang/git2-rs@git2-0.20.2...git2-0.20.4)

---
updated-dependencies:
- dependency-name: git2
  dependency-version: 0.20.4
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Cargo.lock

@@ -17,6 +17,6 @@ structopt = "0.3.26"
 console = "0.16.0"
 tabwriter = { version = "1.4.1"}
 serde_json = { version = "1.0.142"}
-git2 = { version = "0.20.2", default-features = false, features = ["vendored-libgit2"] }
+git2 = { version = "0.20.4", default-features = false, features = ["vendored-libgit2"] }
 serde = { version = "1.0.219", features = ["derive"]}
 phf = { version = "0.12.1", features = ["macros"] }