[ticket/11666] Removing MESSAGE_DELETED..

..in /en/posting.php as it is not used.

PHPBB3-11666
[ticket/11666] Rewording POST_DELETED and

reverting removal of MESSAGE_DELETED.

PHPBB3-11666
Merge branch 'ticket/suheb/11666' into develop-ascraeus

* ticket/suheb/11666:
  [ticket/11666] Rewording POST_DELETED and
  [ticket/11666] Removing MESSAGE_DELETED..