lncfg: mention that taproot chans aren't supported for rbf close

lncfg/protocol.go

@@ -37,7 +37,7 @@ type ProtocolOptions struct {
 
 	// RbfCoopClose should be set if we want to signal that we support for
 	// the new experimental RBF coop close feature.
-	RbfCoopClose bool `long:"rbf-coop-close" description:"if set, then lnd will signal that it supports the new RBF based coop close protocol"`
+	RbfCoopClose bool `long:"rbf-coop-close" description:"if set, then lnd will signal that it supports the new RBF based coop close protocol, taproot channels are not supported"`
 
 	// NoAnchors should be set if we don't want to support opening or accepting
 	// channels having the anchor commitment type.