demo: update to axum-server v0.7.1

Switch to the `tls-rustls-no-provider` feature added in v0.7.1.
Since v0.7.0 the `tls-rustls` feature uses rustls v0.23 which
require a per-process (or thread) `CryptoProvider` be set.
By default, rustls uses `aws_lc_rs` which requires `cmake` et al.
to build. Worse, `axum-server` doesn't re-export the relevant
`rustls` symbols, so one has to declare a direct `rustls` dependency
and keep it in sync to call the required initialization function.

Since this is a basic example, just disable to provider for simplicity.

demo/Cargo.toml

@@ -20,7 +20,7 @@ rand = { version = "0.8.5" }
 rand_core = { version = "0.6.4" }
 ark-ff-macros =  { version = "0.4.2", default-features = false }
 axum = "0.7"  # or the latest version
-axum-server = { version = "0.6", features = ["tls-rustls"] }
+axum-server = { version = "0.7.1", features = ["tls-rustls-no-provider"] }
 tokio = { version = "1", features = ["full"] }
 tracing = "0.1"  # Ensure you have tracing
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }