fix: update axum requirement from 0.6.20 to 0.7.3

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-v0.6.20...axum-v0.7.3)

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

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

Cargo.toml

@@ -35,7 +35,7 @@ shuttle-runtime = { version = "0.31.0", features = ["next", "tracing-subscriber"
 shuttle-axum = { version = "0.31.0" }
 shuttle-secrets = { version = "0.34.0" }
 tokio = { version = "1.33.0", features = ["full"] }
-axum = { version = "0.6.20" }
+axum = { version = "0.7.3" }
 dioxus-fullstack = { version = "0.4", features = ["ssr", "axum", "router"] }
 dioxus-router = { version = "0.4", features = ["ssr"] }