discovery: let reject cache use gossip version in key

Since the gossip protocols are completely disjoint, we need to treat
messages on the two protocols completely separately and should not let
rejections on one protocol affect how we treat messages on the other.

discovery/gossiper_test.go

@@ -4717,6 +4717,7 @@ func TestChanAnnBanningNonChanPeer(t *testing.T) {
 
 	// Remove the scid from the reject cache.
 	key := newRejectCacheKey(
+		ca.GossipVersion(),
 		ca.ShortChannelID.ToUint64(),
 		sourceToPub(nodePeer2.IdentityKey()),
 	)