chore(deps): update axum requirement from 0.7.5 to 0.8.1 (#763)

Updates the requirements on [axum](https://github.com/tokio-rs/axum) to
permit the latest version.
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testimages/Cargo.toml

@@ -6,7 +6,7 @@ publish = false
 
 [dependencies]
 anyhow = "1.0.56"
-axum = { version = "0.7.5", features = ["http2"] }
+axum = { version = "0.8.1", features = ["http2"] }
 tokio = { version = "1.17.0", features = ["full"] }
 
 [build-dependencies]