Language of email notification about creating/deleting answers in Q&A topic should correspond to the chosen language of the subscribed user

Pre-condition:
1. At least two users should be created and logged
2. Both of users should have VIEW_TOPICS and CREATE_POST permissions. User 2 should also have DELETE_OWN_POSTS.
3. At least one branches created
4. A branch has Q&A topic
5. User1 should be subscribed on Q&A topic
6. Current language of User1 is English

Check out a correctness of email notification in different languages:
1. English - Your favorite forum has some updates.
2. Russian - На вашем любимом форуме появились обновления.
3. Ukrainian - На Вашому улюбленому форумі з'явились оновлення.