build(deps): update axum requirement from 0.6.20 to 0.7.1

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-v0.6.20...axum-v0.7.1)

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

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

wtransport/Cargo.toml

@@ -31,7 +31,7 @@ wtransport-proto = { version = "0.1.8", path = "../wtransport-proto", features =
 
 [dev-dependencies]
 anyhow = "1.0.71"
-axum = "0.6.20"
+axum = "0.7.1"
 base64 = "0.21.0"
 hyper = "0.14.27"
 pathsearch = "0.2.0"