message: Fix kv:namespace create --preview
diff: @@ -18,7 +18,10 @@ pub fn run(
  kv::validate_target(&target)?;
  validate_binding(binding)?;
  - let title = format!("{}-{}", target.name, binding);
  + let mut title = format!("{}-{}", target.name, binding);
  + if is_preview {
  + title.push_str("_preview");
  + }
  let msg = format!("Creating namespace with title \"{}\"", title);
  message::working(&msg);
  