Remove space from command name completion suggestion. (#2498)

Although convenient, since the user doesn't have to type the space, it could be
a little surprising to users since they may think that was the only completion
in certain completions modes (for example, `cycle`).

crates/nu-cli/src/completion/command.rs

@@ -27,7 +27,7 @@ impl Completer {
             .into_iter()
             .filter(|v| v.starts_with(partial))
             .map(|v| Suggestion {
-                replacement: format!("{} ", v),
+                replacement: v.clone(),
                 display: v,
             })
             .collect();