Update soketto requirement from 0.7.0 to 0.8.0 (#720)

Updates the requirements on [soketto](https://github.com/paritytech/soketto) to permit the latest version.
- [Release notes](https://github.com/paritytech/soketto/releases)
- [Changelog](https://github.com/paritytech/soketto/blob/master/CHANGELOG.md)
- [Commits](paritytech/soketto@v0.7.0...v0.8.0)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

Cargo.toml

@@ -48,7 +48,7 @@ async-std = { version = "1.6", optional = true }
 tokio = { version = "1.0", optional = true, features = ["full"] }
 tokio-stream = { version = "0.1", optional = true }
 tokio-util = { version = "0.7", optional = true, features = ["compat", "io"] }
-soketto = { version = "0.7.0", optional = true }
+soketto = { version = "0.8.0", optional = true }
 ## Shared (WS, HTTP)
 url = { version = "2.1", optional = true }
 ## EIP-1193