Reword user name’s placeholder for missing users.
Reword user name’s placeholder for missing users.

Refs #65.
As suggested by Pfirsichbaeumchen.

Tatoeba/tatoeba2,shashank19gaurav/tatoeba2,Tatoeba/tatoeba2,Tatoeba/tatoeba2,shashank19gaurav/tatoeba2,Tatoeba/tatoeba2,shashank19gaurav/tatoeba2,Tatoeba/tatoeba2,shashank19gaurav/tatoeba2