Update snafu requirement from 0.7 to 0.8

Updates the requirements on [snafu](https://github.com/shepmaster/snafu) to permit the latest version.
- [Changelog](https://github.com/shepmaster/snafu/blob/main/CHANGELOG.md)
- [Commits](shepmaster/snafu@0.7.0...0.7.5)

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

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -14,7 +14,7 @@ futures = "0.3"
 hotshot-types = { git = "https://github.com/EspressoSystems/HotShot.git", tag = "0.5.7.1" }
 serde = { version = "1.0", features = ["derive"] }
 sha2 = "0.10"
-snafu = { version = "0.7", features = ["backtraces"] }
+snafu = { version = "0.8", features = ["backtraces"] }
 tagged-base64 = { git = "https://github.com/EspressoSystems/tagged-base64", tag = "0.3.4" }
 tide-disco = { git = "https://github.com/EspressoSystems/tide-disco.git", tag = "v0.4.6" }
 toml = "0.8"