cmd/geth: remove reference to monitor command (#22844)

'geth monitor' subcommand is no longer supported.

cmd/geth/consolecmd.go

@@ -171,7 +171,7 @@ func remoteConsole(ctx *cli.Context) error {
 
 // dialRPC returns a RPC client which connects to the given endpoint.
 // The check for empty endpoint implements the defaulting logic
-// for "geth attach" and "geth monitor" with no argument.
+// for "geth attach" with no argument.
 func dialRPC(endpoint string) (*rpc.Client, error) {
 	if endpoint == "" {
 		endpoint = node.DefaultIPCEndpoint(clientIdentifier)