`temporarily_closed_due_to_flags` notice not in server's locale

Bug
1

Priority/Severity: normal

Platform: all

Description: temporarily_closed_due_to_flags notice is not created in server’s locale.

Reproducible steps:

  1. create a topic and
  2. let a lot of users (with locale settings different from server’s locale) flag the posts of the topic. Then
  3. the temporarily_closed_due_to_flags notice (“This topic is temporarily closed for at least %{count} hour due to a large number of community flags.” in en_US locale) created by @system is in user’s locale instead of the server’s.

It’s similar to what this commit has fixed.

I believe it could be fixed by changing the following code.