With the way `dev.ppy.sh` was previously configured, the `osu-web`
`/multiplayer` routes and `osu-server-spectator` `/multiplayer` routes
would conflict with each other, with the `osu-server-spectator` route
taking precedence. This would mean that some `osu-web` pages would just
straight up not be available on dev.
To counteract this, the `osu-server-spectator` routes are now exposed
under `https://dev.ppy.sh/signalr/`. This PR updates the client-side
configuration to use these new routes.
