Update rand requirement from 0.7.3 to 0.8.0

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@0.7.3...0.8.0)

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

Cargo.toml

@@ -21,7 +21,7 @@ required-features = ["build-binary"]
 base64 = "0.13.0"
 peg = "0.6.3"
 proptest = "0.10.1"
-rand = "0.7.3"  # intentionally not upgrading to avoid ./target/... path collision warning
+rand = "0.8.0"  # intentionally not upgrading to avoid ./target/... path collision warning
 serde = { version = "1.0.118", features = ["derive"] }
 structopt = { version = "0.3.21", optional = true }
 test-strategy = "0.1.1"