repl: remove unused err argument

Not used by any callers in `lib/repl.js`, and is not public API.

PR-URL: https://github.com/nodejs/node/pull/16152
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/repl.js

@@ -1025,9 +1025,7 @@ function complete(line, callback) {
 
   // Will be called when all completionGroups are in place
   // Useful for async autocompletion
-  function completionGroupsLoaded(err) {
-    if (err) throw err;
-
+  function completionGroupsLoaded() {
     // Filter, sort (within each group), uniq and merge the completion groups.
     if (completionGroups.length && filter) {
       var newCompletionGroups = [];