make NotificationStream event naming consistent (#4712)

substrate/client/network/src/behaviour.rs

@@ -144,9 +144,9 @@ Behaviour<B, S, H> {
 						roles,
 					}));
 				},
-			CustomMessageOutcome::NotificationsStreamClosed { remote, protocols } =>
+			CustomMessageOutcome::NotificationStreamClosed { remote, protocols } =>
 				for engine_id in protocols {
-					self.events.push(BehaviourOut::Event(Event::NotificationsStreamClosed {
+					self.events.push(BehaviourOut::Event(Event::NotificationStreamClosed {
 						remote: remote.clone(),
 						engine_id,
 					}));

substrate/client/network/src/protocol.rs

@@ -1792,7 +1792,7 @@ pub enum CustomMessageOutcome<B: BlockT> {
 	/// Notification protocols have been opened with a remote.
 	NotificationStreamOpened { remote: PeerId, protocols: Vec<ConsensusEngineId>, roles: Roles },
 	/// Notification protocols have been closed with a remote.
-	NotificationsStreamClosed { remote: PeerId, protocols: Vec<ConsensusEngineId> },
+	NotificationStreamClosed { remote: PeerId, protocols: Vec<ConsensusEngineId> },
 	/// Messages have been received on one or more notifications protocols.
 	NotificationsReceived { remote: PeerId, messages: Vec<(ConsensusEngineId, Bytes)> },
 	None,
@@ -1931,7 +1931,7 @@ Protocol<B, S, H> {
 			LegacyProtoOut::CustomProtocolClosed { peer_id, .. } => {
 				self.on_peer_disconnected(peer_id.clone());
 				// Notify all the notification protocols as closed.
-				CustomMessageOutcome::NotificationsStreamClosed {
+				CustomMessageOutcome::NotificationStreamClosed {
 					remote: peer_id,
 					protocols: self.registered_notif_protocols.iter().cloned().collect(),
 				}

substrate/client/network/src/protocol/event.rs

@@ -61,7 +61,7 @@ pub enum Event {
 
 	/// Closed a substream with the given node. Always matches a corresponding previous
 	/// `NotificationStreamOpened` message.
-	NotificationsStreamClosed {
+	NotificationStreamClosed {
 		/// Node we closed the substream with.
 		remote: PeerId,
 		/// The concerned protocol. Each protocol uses a different substream.