Update rand requirement from 0.7.2 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](https://github.com/rust-random/rand/compare/0.7.2...0.8.0)

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

Cargo.toml

@@ -25,7 +25,7 @@ http = "0.2"
 httparse = "1.3.4"
 input_buffer = "0.3.0"
 log = "0.4.8"
-rand = "0.7.2"
+rand = "0.8.0"
 sha-1 = "0.9"
 url = "2.1.0"
 utf-8 = "0.7.5"