Make GSOC trac read-only

It’s getting pentested: https://gsoc.trac.wordpress.org/ticket/386

Can we make it read-only, and if not, then maybe back it up and shut it down, or put it behind proxy auth or something? It’d be nice to preserve the content for history, but it’s probably not worth maintaining anymore, and definitely not worth cleaning up after pentesters.

#prio3