added Fetch protocol link to IPNS-over-PubSub spec

Author: aschmahmann

naming/pubsub.md

@@ -51,7 +51,7 @@ where base64url-unpadded is an unpadded base64url as specified in [IETF RFC 4648
 
 # Layering persistence onto libp2p PubSub
 
-libp2p PubSub does not have any notion of persistent data built into it. However, we can layer persistence on top of PubSub by utilizing [libp2p Fetch](https://github.com/libp2p/specs/).
+libp2p PubSub does not have any notion of persistent data built into it. However, we can layer persistence on top of PubSub by utilizing [libp2p Fetch](https://github.com/libp2p/specs/pull/204).
 
 The protocol has the following steps:
 1. Start State: Node `A` subscribes to the PubSub topic `t` corresponding to the local IPNS record key `k`