switch the last crate (gix-package-tests) to edition 2021

Author: Byron

gix-pack/tests/Cargo.toml

@@ -5,7 +5,7 @@ repository = "https://github.com/Byron/gitoxide"
 authors = ["Sebastian Thiel <[email protected]>"]
 license = "MIT OR Apache-2.0"
 description = "Please use `gix-<thiscrate>` instead ('git' -> 'gix')"
-edition = "2018"
+edition = "2021"
 rust-version = "1.65"
 
 [features]