fix: rename chain nyx (#56)

Author: euharrison

_IBC/namada-nym.json renamed to _IBC/namada-nyx.json

@@ -6,7 +6,7 @@
     "connection_id": "connection-7"
   },
   "chain_2": {
-    "chain_name": "nym",
+    "chain_name": "nyx",
     "client_id": "07-tendermint-20",
     "connection_id": "connection-10"
   },