[ticket/11346] Hide "Mark topics read" link when forum is empty.

See https://github.com/phpbb/phpbb/pull/919 for some background info.

The two blocks had already diverged when prosilver was initially commited: https://github.com/phpbb/phpbb/blob/f610ed82cbf0df2b5f8afd6ca3f88b9313281036/phpBB/styles/prosilver/template/viewforum_body.html

The logic for the bottom block simply makes no sense and I see no reason for it to be different from the top one. TOTAL_POSTS and TOTAL_USERS are undefined in viewforum.php and simply do not make any sense in this context. I have removed the `<!-- IF .pagination or TOTAL_POSTS or TOTAL_TOPICS -->` check because it's not necessary. There is always content inside `<div class="pagination">` as TOTAL_TOPICS and PAGE_NUMBER will have a value even when the forum is empty. For this same reason `<!-- IF TOTAL_TOPICS -->` is also not needed.

PHPBB3-11346