clan/{id} was removed, but game-client still uses it

[fcaps]

The game-client (chat -> right click on a user -> visit clan page) is opening the clan-page with https://clans.faforever.com/clan/{id}, but this route was removed.
There was some redirect in the code, but it got also removed with #410 .

// Compatibility
app.get('/clan/*', function (req, res){
  const id = req.path.split('/').slice(-1)[0];
  res.redirect('/clans/see?id='+id);
});

there is an issues open, but i would not opt to replace id with tag, just update the route clans with an s.

Till implemented in the game-client, we can enable the redirect again (when clans are working).