rpc: add forgotten 'address' entity to validEntities

The `address` entity is used by the `WalletKit` sub-server for certain
calls.

rpcserver.go

@@ -191,6 +191,7 @@ var (
 	validEntities = []string{
 		"onchain", "offchain", "address", "message",
 		"peers", "info", "invoices", "signer", "macaroon",
+		"address",
 	}
 )