req/resp: use IfDisconnected::ImmediateError (#4253)

* req/resp: use IfDisconnected::ImmediateError

* remove outdated comments

* fmt

polkadot/node/network/availability-distribution/src/requester/fetch_task/mod.rs

@@ -327,7 +327,7 @@ impl RunningTask {
 
 		self.sender
 			.send(FromFetchTask::Message(AllMessages::NetworkBridge(
-				NetworkBridgeMessage::SendRequests(vec![requests], IfDisconnected::TryConnect),
+				NetworkBridgeMessage::SendRequests(vec![requests], IfDisconnected::ImmediateError),
 			)))
 			.await
 			.map_err(|_| TaskError::ShuttingDown)?;

polkadot/node/network/availability-distribution/src/requester/fetch_task/tests.rs

@@ -230,7 +230,7 @@ impl TestRun {
 		match msg {
 			AllMessages::NetworkBridge(NetworkBridgeMessage::SendRequests(
 				reqs,
-				IfDisconnected::TryConnect,
+				IfDisconnected::ImmediateError,
 			)) => {
 				let mut valid_responses = 0;
 				for req in reqs {