Update peg requirement from ~0.7 to ~0.8

Updates the requirements on [peg](https://github.com/kevinmehall/rust-peg) to permit the latest version.
- [Release notes](https://github.com/kevinmehall/rust-peg/releases)
- [Commits](https://github.com/kevinmehall/rust-peg/compare/0.7.0...0.8.0)

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

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

edn/Cargo.toml

@@ -18,7 +18,7 @@ pretty = "~0.10"
 uuid = { version = "~1.0", features = ["v4", "serde"] }
 serde = { version = "~1.0", optional = true }
 serde_derive = { version = "~1.0", optional = true }
-peg = "~0.7"
+peg = "~0.8"
 bytes = "1.0.1"
 hex = "0.4.3"