Make unbounded channels size warning exact (part 2) (#13504)

substrate/client/service/src/task_manager/mod.rs

@@ -281,7 +281,7 @@ impl SpawnEssentialTaskHandle {
 		let essential_failed = self.essential_failed_tx.clone();
 		let essential_task = std::panic::AssertUnwindSafe(task).catch_unwind().map(move |_| {
 			log::error!("Essential task `{}` failed. Shutting down service.", name);
-			let _ = essential_failed.close_channel();
+			let _ = essential_failed.close();
 		});
 
 		let _ = self.inner.spawn_inner(name, group, essential_task, task_type);