(I don't think this string warrants deprecation)
$string['taskcachecron'] = 'Background processing for caches';
$string['taskcalendarcron'] = 'Send calendar notifications';
$string['taskcheckforupdates'] = 'Check for updates';
-$string['taskcompletioncron'] = 'Calculate completion data';
$string['taskcompletionregular'] = 'Calculate regular completion data';
$string['taskcompletiondaily'] = 'Completion mark as started';
$string['taskcontextcleanup'] = 'Cleanup contexts';