completion MDL-24119 new string that was previously in the code

lang/en/completion.php

@@ -91,6 +91,7 @@
 $string['approval']='Approval';
 $string['completionenabled']='Enabled, control via completion and activity settings';
 $string['completionmenuitem']='Completion';
+$string['completiononunenrolment']='Completion on unenrolment';
 $string['completionsettingslocked']='Completion settings locked';
 $string['completionstartonenrol']='Completion tracking begins on enrolment';
 $string['completionstartonenrolhelp']='Begin tracking a student\'s progress in course completion after course enrolment';