Hardcoded "operation" language string in backup async helper

The string 

 asyncmessagebodydefault | core_backup 

with the text:

Hi {user_firstname},​<br/> Your {operation} (ID: {backupid}) has completed successfully. <br/><br/>You can access it here: {link}.

contains a hard coded word.

What shows up for the string {operation} can't be translated.

The same goes for the subject line: asyncmessagesubjectdefault | core_backup 

Moodle {operation} completed successfully

These are the only occurences of {operation} in the language pack, so I think that should be all.

Steps to reproduce:

1. Change your default language to something else then English
2. Duplicate a course
3. The notification email that is send when the copy is done, will contain the word "copy" in English, both in subject and body.

I can't find the strings for what goes in "operation" for the Dutch language pack. It's 100% complete.