Update axum requirement from 0.6.0-rc.2 to 0.8.0-alpha.1

Updates the requirements on [axum](https://github.com/tokio-rs/axum) to permit the latest version.
- [Release notes](https://github.com/tokio-rs/axum/releases)
- [Changelog](https://github.com/tokio-rs/axum/blob/main/CHANGELOG.md)
- [Commits](tokio-rs/axum@axum-v0.6.0-rc.2...axum-v0.8.0-alpha.1)

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

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

Cargo.toml

@@ -22,4 +22,4 @@ http-body = "0.4"
 tokio = { version = "1", features = ["full"] }
 hyper = { version = "0.14", features = ["full"] }
 tower = { version = "0.4", features = ["full"] }
-axum = "0.6.0-rc.2"
+axum = "0.8.0-alpha.1"