blog.archive: Don't silently hide half of the recent posts

When the [:recents :total] key is defined in the config, we dropped
that many from the archived posts, even though it only displayed rows
* columns number of them, which, in this case, can be a different
number.

Instead, drop rows * columns number of elements when displaying the
archived posts, thereby showing the full archive.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>