[ticket/11672] Removed unnecessary text from alerts.

Messages like "Return to forum last visited" are entirely unnecessary
when using AJAX to delete a post, so this commit removes them.

PHPBB3-11672
[ticket/11672] Replace sprintf() usage with $user->lang().

PHPBB3-11672
[ticket/11672] Remove some messages that were missed in mcp_queue.php.

PHPBB3-11672
[ticket/11672] Clean up the logic in mcp_queue.php.

PHPBB3-11672
[ticket/11672] Remove the messages for lock/unlock/change topic type.

PHPBB3-11672
[ticket/11672] The json response call exits so the else is not necessary.

PHPBB3-11672
[ticket/11672] Remove duplicate $request global.

PHPBB3-11672
Merge remote-tracking branch 'prototech/ticket/11672' into develop

* prototech/ticket/11672:
  [ticket/11672] Remove duplicate $request global.
  [ticket/11672] The json response call exits so the else is not necessary.
  [ticket/11672] Remove the messages for lock/unlock/change topic type.
  [ticket/11672] Clean up the logic in mcp_queue.php.
  [ticket/11672] Remove some messages that were missed in mcp_queue.php.
  [ticket/11672] Replace sprintf() usage with $user->lang().
  [ticket/11672] Removed unnecessary text from alerts.
  [ticket/11814] Remove redundant text from the topic reply email notification.