Remove alias for no-input

Apparently, kong `aliases` are only for commands. It did not work as I
had expected. At this point, `--no-input` has been removed. If we want
to keep it for backwards compatibility, I suppose we could add a new
hidden command line arg called `--no-input`. I defer to you for your
thoughts.

main.go

@@ -32,7 +32,7 @@ var root struct {
 
 	NotebookDir string  `type:path placeholder:PATH help:"Turn off notebook auto-discovery and set manually the notebook where commands are run."`
 	WorkingDir  string  `short:W type:path placeholder:PATH help:"Run as if zk was started in <PATH> instead of the current working directory."`
-	NoInput     NoInput `name:"no-prompt" aliases:"no-input" help:"Never prompt or ask for confirmation."`
+	NoInput     NoInput `name:"no-prompt" help:"Never prompt or ask for confirmation."`
 	// ForceInput is a debugging flag overriding the default value of interaction prompts.
 	ForceInput string `hidden xor:"input"`
 	Debug      bool   `default:"0" hidden help:"Print a debug stacktrace on SIGINT."`