build(deps): bump rand from 0.7.3 to 0.8.1

Bumps [rand](https://github.com/rust-random/rand) from 0.7.3 to 0.8.1.
- [Release notes](https://github.com/rust-random/rand/releases)
- [Changelog](https://github.com/rust-random/rand/blob/master/CHANGELOG.md)
- [Commits](rust-random/rand@0.7.3...0.8.1)

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

Author: dependabot-preview[bot]

Cargo.lock

@@ -31,6 +31,6 @@ r-efi = "3.2.0"
 uart_16550 = "0.2.10"
 
 [dev-dependencies]
-rand = "0.7.3"
+rand = "0.8.1"
 ssh2 = "0.8.3"
 tempfile = "3.1.0"