Update criterion requirement from 0.3 to 0.4

Updates the requirements on [criterion](https://github.com/bheisler/criterion.rs) to permit the latest version.
- [Release notes](https://github.com/bheisler/criterion.rs/releases)
- [Changelog](https://github.com/bheisler/criterion.rs/blob/master/CHANGELOG.md)
- [Commits](bheisler/criterion.rs@0.3.0...0.4.0)

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

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

xtra/Cargo.toml

@@ -39,7 +39,7 @@ smol = "1.1"
 smol-potat = "1.1"
 smol-timeout = "0.6"
 waker-fn = "1.1"
-criterion = { version = "0.3", features = ["async_tokio"] }
+criterion = { version = "0.4", features = ["async_tokio"] }
 tokio = { version = "1.0", features = ["full"] }
 async-std = { version = "1.0", features = ["attributes"] }
 tracing = { version = "0.1.35", features = ["std"] }