Update axum requirement from 0.7.9 to 0.8.1

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](https://github.com/tokio-rs/axum/commits)

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

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

Cargo.toml

@@ -38,7 +38,7 @@ serde_json = "1.0.120"
 jiff = { version = "0.1.4", features = ["serde"] }
 tokio = { version = "1.37.0", features = ["macros", "test-util", "rt-multi-thread"] }
 # Used in examples
-axum = "0.7.9"
+axum = "0.8.1"
 svix = "1.42.0"
 http-body-util = "0.1.2"
 tokio-shared-rt = "0.1.0"