net/quinn: Fix test panic due to unset default crypto provider

If another dep in the workspace pulls in a different rustls crypto
provider then we need to explicitly specify our default provider.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1801>

net/quinn/tests/quinnquic.rs

@@ -18,6 +18,9 @@ fn init() {
     INIT.call_once(|| {
         gst::init().unwrap();
         gstquinn::plugin_register_static().expect("QUIC source sink send receive tests");
+        rustls::crypto::ring::default_provider()
+            .install_default()
+            .expect("Failed to install ring crypto provider");
     });
 }