Update rand_core requirement from 0.6 to 0.9

Updates the requirements on [rand_core](https://github.com/rust-random/rand) to permit the latest version.
- [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...0.9.0)

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

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

Cargo.toml

@@ -34,7 +34,7 @@ elliptic-curve = { version = "0.13", features = [
   "voprf",
 ] }
 generic-array = "0.14"
-rand_core = { version = "0.6", default-features = false }
+rand_core = { version = "0.9", default-features = false }
 serde = { version = "1", default-features = false, features = [
   "derive",
 ], optional = true }