Email received in different language if the sender has different language preference

Email notification in mix language if the sender and recipient has different language preference.
The event type is not translated, everything else appears to be.

Step to reproduce:

1. create two users with different language preference(eg: Sender using English, Recipient using German)
2. login as the German speaker user and create issue.
3. notification received in German as shown in the screenshot FullGermanLang.png
4. login as English Speaker user
5. create and issue and the notification send to both user ( assuming that they are either Reporter or Assignee of the ticket)
6. German user will received a mix language email as shown in HalfGermanLang.png