⬆️ Update insta requirement from 0.7 to 0.8

Updates the requirements on [insta](https://github.com/mitsuhiko/insta) to permit the latest version.
- [Release notes](https://github.com/mitsuhiko/insta/releases)
- [Commits](mitsuhiko/insta@0.7.0...0.8.1)

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

Cargo.toml

@@ -24,7 +24,7 @@ failure = "0.1"
 
 [dev-dependencies]
 test-generator = "0.2"
-insta = "0.7"
+insta = "0.8"
 serde = { version = "1.0", features = [ "derive" ] }
 serde_json = "1.0"
 criterion = "0.2"