Title language of "Highlight" button is english when user switches language to russian

Preconditions: "Test user" should have permissions for send private message

Steps to reproduce

1. Open jcommune -> Login as "Test user"
2. Choose russian language for browsing the page
3. Go to private message -> go to create new message
4. Take a look on "Highlight" button

AR: Title of "Highlight" button is "Highlight"
ER: Title of "Highlight" button is "Подсветка"

Notes: The same situation with ukrainian, spanish languages and with ukrainian, spanish languages when user creates new topic