don't display old thread info in threads-view
don't display old thread info in threads-view

addresses https://github.com/braidchat/meta/issues/568

Previously, when trying to maintain order of threads, the old threads
would stay in the threads list, which meant that if the tags changed the
thread wouldn't be updated & the limbo/private banners would stay above
the thread. To fix, calculate the order of threads in the same way, but
use new-threads as the actual data

braidchat/braid,braidchat/braid,rafd/braid,rafd/braid