should use ...$spans instead of $spans in carapace completer (#1399)

cookbook/external_completers.md

@@ -114,7 +114,7 @@ The solution to this involves manually checking the value to filter it out:
 
 ```nu
 let carapace_completer = {|spans: list<string>|
- carapace $spans.0 nushell $spans
+ carapace $spans.0 nushell ...$spans
  | from json
  | if ($in | default [] | where value == $"($spans | last)ERR" | is-empty) { $in } else { null }
 }