Update rand_core requirement

Updates the requirements on [rand_core](https://github.com/rust-random/rand) to permit the latest version.

Updates `rand_core` to 0.6.4
- [Release notes](https://github.com/rust-random/rand/releases)
- [Changelog](https://github.com/rust-random/rand/blob/master/CHANGELOG.md)
- [Commits](rust-random/rand@rand_core-0.6.0...rand_core-0.6.4)

---
updated-dependencies:
- dependency-name: rand_core
  dependency-type: direct:production
  dependency-group: dependencies
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Cargo.toml

@@ -18,7 +18,7 @@ clap = { version = "4.4", features = ["derive"] }
 ed25519-dalek = { version = "2", features = ["digest"] }
 normalize-path = "0.2"
 pretty-error-debug = "0.3"
-rand_core = { version = "0.6", features = ["getrandom"] }
+rand_core = { version = "0.9", features = ["getrandom"] }
 tempfile = "3"
 thiserror = "1"
 zip = { version = "2", default-features = false }