Update smol requirement from 1 to 2

Updates the requirements on [smol](https://github.com/smol-rs/smol) to permit the latest version.
- [Release notes](https://github.com/smol-rs/smol/releases)
- [Changelog](https://github.com/smol-rs/smol/blob/master/CHANGELOG.md)
- [Commits](smol-rs/smol@v1.0.0...v2.0.0)

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

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

Cargo.toml

@@ -22,4 +22,4 @@ futures-io = "0.3.5"
 
 [dev-dependencies]
 futures = { version = "0.3.5", default-features = false, features = ["std"] }
-smol = "1"
+smol = "2"