[ticket/12768] 'NOTIFICATION_REPORT_CLOSED' entry has wrong indentation

'NOTIFICATION_REPORT_CLOSED' has 3 spaces before the first tab indentation
in language/en/common.php.

PHPBB3-12768
[ticket/12768] More fixes in language files

More spaces converted to tabs for identation in language files.

PHPBB3-12768
Merge pull request #2713 from n-aleha/ticket/12768

[ticket/12768] 'NOTIFICATION_REPORT_CLOSED' entry has wrong indentation

* n-aleha/ticket/12768:
  [ticket/12768] More fixes in language files
  [ticket/12768] 'NOTIFICATION_REPORT_CLOSED' entry has wrong indentation