make it obvious that unbounded channels don't need to await, and tidy up some bits

backend/telemetry_core/tests/basic_tests.rs

@@ -1,3 +1,5 @@
+#![cfg(feature = "e2e")]
+
 use test_utils::{feed_message_de::FeedMessage, server::Server};
 // use serde_json::json;
 
@@ -24,4 +26,4 @@ async fn can_ping_feed() {
 
     // Tidy up:
     server.shutdown().await;
-}
+}