Update rand requirement from 0.7 to 0.8

Updates the requirements on [rand](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@0.7.0...0.8.0)

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

Author: dependabot-preview[bot]

Cargo.toml

@@ -29,7 +29,7 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 
 interpolation = "0.2"
-rand = "0.7"
+rand = "0.8"
 
 svg = "0.8"