config: Update default cashier public key.

example/config/darkfid.toml

@@ -43,4 +43,4 @@ name = "testnet.cashier.dark.fi"
 rpc_url = "tls://testnet.cashier.dark.fi:9000"
 
 # The selected cashier public key
-public_key = "95MPgrASV5WQ6DgoVaWgamrnCFN3V5FZrJNCUWWhDEKz"
+public_key = "129F9szk9CuMEzBb8VqnoWPuShxayUznAgUBZsGzLyMrkDBHxC3"