Update toml requirement from 0.7 to 0.8

Updates the requirements on [toml](https://github.com/toml-rs/toml) to permit the latest version.
- [Commits](toml-rs/toml@toml-v0.7.0...toml-v0.8.0)

---
updated-dependencies:
- dependency-name: toml
  dependency-type: direct:production
...

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

Cargo.toml

@@ -32,5 +32,5 @@ veil-macros = { path = "veil-macros", version = "=0.1.6" }
 once_cell = "1"
 
 [dev-dependencies]
-toml = "0.7"
+toml = "0.8"
 serde = { version = "1", features = ["derive"] }